Background Surgery may lead to a series of psychological reactions which affect the prognosis and quality of life.Social support,reflecting the connection between individuals and society,might attenuate these psychological disorders.However,the relationship between social support and negative emotions in patients undergoing cardiac surgery is unclear.Methods Self-rating depression scale (SDS),self-rating anxiety scale (SAS) and social support rating scale (SSRS) were applied to 244 patients before cardiac surgery.Data were analyzed using descriptive statistics,factor analysis,mean sum variables and multivariate logistic regression.Results Of the 244 surgical patients,the total incidence of depression was 29.51％ (72/244).Among depressed patients,55 patients (22.54％) were mild,13 (5.33％) were moderate,and 4 (1.64％) were severe.The total incidence of anxiety was 39.75％ (97/244).Among them,69 patients (28.28％) were mild,20 (8.20％) were moderate,and 8 (3.28％) were severe.Social support score was 36.32±8.67,of which objective support scores and subjective support scores in depression group and anxiety group were lower than non-depression group and non-anxiety group respectively (t=-2.621,-2.155,-2.506,-2.171,P＜0.05).Univadate x2 test revealed that depression or anxiety before cardiac surgery was related to gender,marital status,income,hypertension,types of heart disease and social support.Multivariate logistic regression analysis revealed that female,being single,aortic dissection/aneurysm,and low social support were related to depression,and female,age older than 60 years old,single,and low social support were related to anxiety.Conclusions Social support is negatively correlated with depression and anxiety in patients undergoing cardiac surgery.Prior to cardiac surgery,extra attention should be paid to women,single patients,and those demonstrating a lower level of social support.