Sixteen-character formula is the basic achievement method of Qigong Neidan. Also known as "sixteen ingots of gold" or "one-scale gold formula". "Chifeng years old, Li Zhenren's 16-character wonderful prescription longevity": "When inhaling, lift it, and the gas will return to the navel; Swallow when you mention it, and water and fire are incompatible. " And contains specific training methods. This exercise is simple and easy, and it is said that it can achieve better health preservation effect. In addition, the secret book of health preservation, the inner purpose of the Yellow River and pulse observation all contain this technique, and the text is slightly different.