When the initial stage practice of "refining Essence into Qi" yields results, one can further practice "refining Qi into Spirit". "Refining Qi into Spirit" belongs to the "Middle Pass" of the "Three-Stage Practice". Since it takes ten months, it is also called the "Ten-Month Pass". If "refining Essence into Qi" is about unblocking the Ren and Du meridians to make the primordial Qi circulate in the "Small Circulation" (the Ren and Du meridians), then "refining Qi into Spirit" is the practice of the "Great Circulation".

The so-called "Great Circulation" means that the circulation of primordial Qi is no longer limited to the Ren and Du meridians, but can circulate through all twelve meridians. Compared with the "gathering the three into two" in "refining Essence into Qi", "refining Qi into Spirit" is a process of "integrating the two into one", that is, promoting the mutual integration and fusion of "Qi" and "Spirit".

Taoist schools refer to the effect of integrating "Spirit" and "Qi" as the "Sacred Embryo", and in terms of Waidan (External Alchemy) terminology, it is called "the production of the great Elixir". This is a transition from the "active" method to the "non-active" method. It takes the lower Dantian as the furnace and the middle Dantian (Huangting) as the cauldron. The primordial Qi lingers and circulates repeatedly between the lower Dantian ("one and three-tenths inches below the navel") and the middle Dantian ("between the two breasts"). After ten months of nurturing the embryo, it achieves the wonderful effect of the union of Qian (Heaven) and Kun (Earth). Such opening and closing, inhalation and exhalation, seize the creation of heaven and earth and conform to the heavenly mechanism of a year.