Abstract: Objective To study the characteristics of deficiencies of yin and yang among sub-healthy undergraduate students according to the theory of traditional Chinese medicine(TCM).Methods Though field survey, 7 000 undergraduate students in Guangzhou were surveyed with Sub health Self ra ting Sca le(SSS) and the Constitution in Chinese Medicine Question naire(CCM Q).The data were analyzed with frequencies and Chisquare test to explore the correlation between TCM construction and sub-health among the underg raduate students.Results The results showed that the total prevalence rate of sub-health among the students was 62.51%.The preva lence rate of sub-health in the female was significantly higher than that of in the male(P < 0.05).The results also showed that the ratio of biased constitution healthy among the students was 4.20%, while that of sub-healthy was 47.70%.There were statistical significances in the ratios between different 9 TCM constitutions(P < 0.05).There were many psychological and social problems among the sub-health students including the characteristics of dampness heat, blood stasis and insufficiency of the spleen besides the deficiency of yin and deficiency of yang among the sub-healthy students with de ficiency of yin and deficiency of yang.Conclusion There are many psy chological and social problems among sub-health under graduate students and attention should be taken for the students to prevent the occurrence of sub-health.