Objective To explore the relationship between Yin and Yang deficiency syndrome of type 2 diabetes and TCM Constitution of TCM， and provide theoretical basis for the treatment and prevention of TCM syndrome differentiation. Methods A retrospective study was conducted on 2 patients with type 302 diabetes mellitus in our hospital， and the relationship between diabetes mellitus and TCM constitution was analyzed. Results In type 2 diabetes， TCM Constitution， Yin and Yang deficiency syndrome in two main syndrome， Yang deficiency， damp heat， blood stasis and its related， the difference was statistically significant（P<0.05）. Among them， Yang deficiency and damp heat are the risk factors of Yin and Yang two deficiency， blood stasis is the protective factor of Yin and Yang deficiency of Yin and Yang. Conclusion Yin and Yang in TCM Constitution in type 2 diabetes mellitus in two principal syndromes deficiency syndrome principal syndrome， Yang deficiency and damp heat syndrome is a risk factor of two Yin and Yang， blood stasis is a protective factor of two Yin and Yang， to provide new ideas for the prevention and treatment of type 2 diabetes.