Objective:To Survey and research the relationship of Yin(not-manifested)symptoms of traditional chinese medicine and constitution in order to enlarge the category of syndrome differentiatioin of TCM.Methods:The 523 healthy subjects who had the physical check were involved in the observation.According to the theories of the Chinese Medicine constitution theory and the Yin Symptoms of TCM,the data were processed with statistics.Conclusion:Yin symptom of TCM was an objective existence and occupied a relatively high percentage in those who had nosymptom and sign in physical check.The theory of Yin symptom?With the TCM constitution theory will make the category of TCM differen tiation widened and the level of diagnosis enhanced.