Tumor phenotype is an important research method to understand tumors from the microscopic perspective.This paper discussed the concept of tumor phenotype from the theory of yin and yang in traditional Chinese medicine（TCM）

and expounded its’ divisible

nested and universal characters

and classified it into two types of yin excessiveness and yang declining

and two special types of yang in the yin and yin in the yang for identification.It is believed that the imbalance of yin and yang in tumor phenotype is the dynamic phenotype change between yin sufficiency and yang deficiency.It provides a novel insight for "microscopic syndrome differentiation"of tumor guided by the theory of yin and yang.