The dichotomy and the quintomy

based on the yin yang

and five elements theory

are the most commonly used in traditional Chinese medicine（TCM） theory

and the trichotomy method is also commonly found in the theoretical system of Inner Canon of Yellow Emperor（《黄帝内经》）. Through the review of the literature

it is found that the classification method of one-three-dimension runs through all links in the theoretical system of TCM

not only constructin the medical mode of "three dimensions"

but also forming the physical view of "three division of zang-fu organs"

the etiology view of "three part qi"

the diagnosis view of "three body parts and nine pulse taking sites"

and the treatment view of "three factors to different conditions". Deeper understanding of the connotation and theoretical origin of the trichotomy can deepen the understanding of TCM theory.