夫子午流注者刚柔相配阴阳相合气血循环时穴开阖也何以子午言之曰子时一刻乃一阳之生至
午时一刻乃一阴之生故以子午分之而得乎中也流者往也注者住也天干有十经有十二甲胆乙肝
丙小肠丁心戊胃巳脾庚大肠辛肺壬膀胱癸肾余两经者乃三焦包络也三焦乃阳气之父包络乃阴
血之母此二经虽奇于壬癸亦分派于十干且每经之中有井荣俞经合以配金水木火土是故阴井木
而阳井金阴荣火而阳荣水阴俞土而阳俞木阴经金而阳经火阴合水而阳合土矣经中又有返本还
原者乃十二经出入之门户也阳经有原遇俞穴并过之阴经无原以俞穴即代之是以甲出丘墟乙太
冲之例又按千金云六阴经亦有原穴乙中都丁通里巳公孙辛列缺癸水泉包络内关也故阳日气先
行而血后随也阴日血先行而气后随也得时为之开失时为之阖阳干注腑甲丙戊庚壬而重见者气
纳
并过胆原重见甲申时气纳三焦荣穴属水甲属木是以水生木谓甲合还元化木又如乙酉时以开肝
井至己丑时当脾之俞井过肝原重见乙未时血纳包络荣穴属火乙属木是以木生火也余皆根据此俱
以子母相生阴阳相济也阳日无阴时阴日无阳时故甲与己合乙与庚合丙与辛合丁与壬合戊与癸
合也何以甲与合曰中央戊己属土畏东方甲乙之木所克戊方阳为兄己属阴为妹戊兄遂将己妹嫁
与木家于甲为妻庶得阴阳和合而不相伤所以甲与己合余皆然子午之法尽于此矣
所谓子午流注，是指天干地支的刚柔相配、阴阳相合，以及气血在特定时间穴位中的开阖循环。为什么要用“子”和“午”来命名呢？因为子时（夜间11点至凌晨1点）的一刻是阳气初生之时，而午时（中午11点至下午1点）的一刻是阴气初生之时，所以以子午来划分，正好处于阴阳平衡的中点。“流”意为流动，“注”意为灌注或停留。
天干有十个，经脉有十二条。甲对应胆，乙对应肝；丙对应小肠，丁对应心；戊对应胃，己对应脾；庚对应大肠，辛对应肺；壬对应膀胱，癸对应肾。剩下的两条经脉是三焦经和心包络经。三焦经是阳气的父亲，心包络经是阴血的母亲。这两条经脉虽然不同于壬癸所对应的脏腑，但也分属于十天干之中。而且每一条经脉中都有井穴、荥穴、输穴、经穴、合穴这五类穴位，分别配合金、水、木、火、土五行。因此，阴经的井穴属木，而阳经的井穴属金；阴经的荥穴属火，而阳经的荥穴属水；阴经的输穴属土，而阳经的输穴属木；阴经的经穴属金，而阳经的经穴属火；阴经的合穴属水，而阳经的合穴属土。
经脉中还有“返本还原”的说法，这是指十二经脉出入的门户。阳经有原穴，经过输穴时会同时经过原穴；阴经没有单独的原穴，就以输穴代替原穴。例如，甲胆经出于丘墟穴，乙肝经出于太冲穴。另外根据《千金方》记载，六条阴经也有原穴：乙肝经的原穴是中都，丁心经的原穴是通里，己脾经的原穴是公孙，辛肺经的原穴是列缺，癸肾经的原穴是水泉，心包络经的原穴是内关。
所以在阳日，气先行而血随后跟随；在阴日，血先行而气随后跟随。得时则穴位开放，失时则穴位闭合。阳干注入腑，即甲、丙、戊、庚、壬。当重见（重复出现）时，气纳入并过原穴。例如，胆经（甲）重见于甲申时，气纳入三焦经的荥穴（属水），甲属木，水生木，称为“甲合还元化木”。又如，肝经（乙）重见于乙未时，血纳入心包络经的荥穴（属火），乙属木，木生火。其余情况都依据此理，都是根据母子相生、阴阳相济的原则。
阳日没有阴时，阴日没有阳时，所以甲与己合，乙与庚合，丙与辛合，丁与壬合，戊与癸合。为什么甲与己合呢？因为中央的戊己属土，畏惧东方甲乙之木的克制。戊为阳土为兄，己为阴土为妹，戊兄便将己妹嫁给木家（甲）为妻，从而使得阴阳和合而不相伤害，所以甲与己相合。其余各对也都遵循这一道理。子午流注的方法就到这里了。
The method of Zi Wu Liu Zhu (Midnight-Noon Ebb-Flow) refers to the matching of rigidity and softness between Heavenly Stems and Earthly Branches, the harmony of Yin and Yang, and the opening and closing cycles of Qi and Blood in specific acupoints at designated times. Why are "Zi" (Rat hour) and "Wu" (Horse hour) used for this designation? Because at the beginning of the Zi hour (11:00 PM - 1:00 AM), Yang Qi begins to generate; and at the beginning of the Wu hour (11:00 AM - 1:00 PM), Yin Qi begins to generate. Therefore, dividing by Zi and Wu achieves a balance in the middle. "Liu" (Flow) means movement, and "Zhu" (Pour/Stop) means infusion or residence.
There are ten Heavenly Stems and twelve Meridians. Jia corresponds to the Gallbladder, Yi to the Liver; Bing to the Small Intestine, Ding to the Heart; Wu to the Stomach, Ji to the Spleen; Geng to the Large Intestine, Xin to the Lungs; Ren to the Bladder, Gui to the Kidneys. The remaining two meridians are the Sanjiao (Triple Burner) and the Pericardium (Bao Luo). The Sanjiao is considered the father of Yang Qi, and the Pericardium is the mother of Yin Blood. Although these two meridians differ from those associated with Ren and Gui, they are also distributed among the Ten Stems. Furthermore, within each meridian, there are five categories of acupoints: Jing-Well, Ying-Spring, Shu-Stream, Jing-River, and He-Sea, which correspond to the Five Elements Metal, Water, Wood, Fire, and Earth. Thus, the Jing-Well point of Yin meridians belongs to Wood, while that of Yang meridians belongs to Metal; the Ying-Spring point of Yin meridians belongs to Fire, while that of Yang meridians belongs to Water; the Shu-Stream point of Yin meridians belongs to Earth, while that of Yang meridians belongs to Wood; the Jing-River point of Yin meridians belongs to Metal, while that of Yang meridians belongs to Fire; and the He-Sea point of Yin meridians belongs to Water, while that of Yang meridians belongs to Earth.
Within the meridians, there is also the concept of "Returning to the Root and Restoring the Origin," which serves as the gateway for the entry and exit of the Twelve Meridians. Yang meridians have Yuan-Source points; when passing through the Shu-Stream points, they simultaneously pass through the Yuan-Source points. Yin meridians do not have separate Yuan-Source points, so the Shu-Stream points serve as substitutes. For example, the Jia Gallbladder meridian originates from Qiuxu (GB40), and the Yi Liver meridian originates from Taichong (LR3). Additionally, according to the *Qianjin Fang* (Thousand Gold Formulas), the six Yin meridians also have Yuan-Source points: Zhongdu (LR6) for the Yi Liver, Tongli (HT5) for the Ding Heart, Gongsun (SP4) for the Ji Spleen, Lieque (LU7) for the Xin Lung, Shuiquan (KI5) for the Gui Kidney, and Neiguan (PC6) for the Pericardium.
Therefore, on Yang days, Qi moves first and Blood follows; on Yin days, Blood moves first and Qi follows. When the time is appropriate, the acupoint opens; when the time is missed, it closes. Yang Stems inject into the Fu organs, namely Jia, Bing, Wu, Geng, and Ren. When a stem repeats (reappears), Qi is stored in the Sanjiao's Ying-Spring point and passes through the Yuan-Source point. For instance, when the Gallbladder (Jia) repeats at the Jia-Shen hour, Qi enters the Sanjiao's Ying-Spring point (belonging to Water). Since Jia belongs to Wood, Water generates Wood, referred to as "Jia combines and returns to transform into Wood." Similarly, when the Liver (Yi) repeats at the Yi-Wei hour, Blood enters the Pericardium's Ying-Spring point (belonging to Fire). Since Yi belongs to Wood, Wood generates Fire. All other cases follow this principle, based on the generation of Mother and Child elements and the mutual complementarity of Yin and Yang.
Yang days lack Yin hours, and Yin days lack Yang hours. Therefore, Jia combines with Ji, Yi with Geng, Bing with Xin, Ding with Ren, and Wu with Gui. Why does Jia combine with Ji? Because Wu and Ji in the Center belong to Earth, which fears being controlled by the Wood of Jia and Yi in the East. Wu is Yang Earth (older brother), and Ji is Yin Earth (younger sister). The older brother Wu marries off his younger sister Ji to the Wood family (Jia) as a wife, thereby achieving harmony between Yin and Yang without mutual harm. Hence, Jia combines with Ji. The same logic applies to the others. This concludes the explanation of the Zi Wu method.