Objective To study the objective existence of Yin（not-yet-manifested）symptoms of Traditional Chinese Medicine in order to enlarge the category of syndrome differentiation of TCM.Methods The 615 healthy subjects who had the physical check were involved in the observation.According to the theories of Zangxiang（viscera manifestation）and Qi

Blood and Body Fluid of TCM

the abnormal findings of those who had no symptoms were divided into Zangfu（viscera）Yin（not-yet-manifested）symptoms（including the heart Yin symptoms

liver and gall bladder Yin symptoms

spleen and stomach Yin symptoms

lung Yin symptoms

and kidney Yin symptoms）and Qi

Blood and Body Fluid Yin symptoms.The data were processed with statistics.Results Totally 197 items were found abnormal and the 119 cases were found to be Yin symptom patients.Of them

there were 57 heart Yin symptom patients

51 liver and gall bladder Yin symptom patients

6 spleen and stomach Yin symptom patients

4 lung Yin symptom patients

17 kidney Yin symptom patients

and 31 Qi

Blood and Body Fluid Yin symptom patients.Conclusion Yin symptom of TCM was an objective existence and occupied a relatively high percentage in those who had no symptom and sign in physical check.The theory of Yin symptom will make the category of TCM differentiation widened and the level of diagnosis enhanced.