The mathematical logic of Chinese classical philosophy has experienced the evolution process of “one”“two”and “three”. Everything originated from“one”,that is monism. Everything is unified,and everything is in a lifetime；from one to two,there is yin and yang,that isbinary (dualism)；two begets three,things begin to be many,this is ternary (ternism),“three” means the diversity of the universe. Rooting deeply in the soil of Chinese classical philosophy,ternary mode is ultimately applied in the theoretical system of traditional Chinese medicine to interpret how life happens,human anatomy,physiology,the etiology and pathogenesis,theories of materiamedica,etc.Therefore,“ternary system” is the key to open the door of traditional Chinese medicine.