The spleen, stomach, large intestine, small intestine, triple energizer, and bladder are collectively referred to as Zhi Yin in Huangdi Neijing, which is connecting with Earth Qi and depends on gallbladder. "Mean and Harmony" is an important feature of Earth by analogy. Based on the metaphor of the concept of "Mean and Harmony", this paper uses the reasoning tools of Yin-Yang, Five Elements, Qi, Blood and Body Fluid to analyze the essence and interpretation dimension of "Zhi Yin" and "Connecting with Earth Qi", and points out these related to the acceptance and transportation, sleep and wake up, qi rise and fall, prevention and regulation, which is helpful to correctly understand the classic theory, highlight the importance of the classic, and then guide clinical application.