The problem of social anxiety among Chinese undergraduates is serious. Previous studies have indicated that social anxiety was more prone to occur among lower-class individuals. However, the psychological mechanism has not been fully explored yet. Social cognitive theory of social class interprets the association between individuals’ social class and healthy condition, which proposes that lower-class individuals are much easier to be influenced by external environment because they have less supports and more threats. Thus, they have higher threat sensitivity and more negative emotions. Additionally, the reserve capacity model showed the effect and mechanisms of social class on individuals’ health conditions. According to reserve capacity model, psychosocial resources are tangible, interpersonal and intrapersonal energy that can be used to cope with daily life pressure. Unfortunately, lower-class environment may expose individuals to more stressors while equipping them with less psychosocial resources. Therefore, we hypothesized the multiple mediating effects of psychosocial resources and threat sensitivity between social class and mental health. The present study aimed to testify the multiple mediating effects of psychosocial resources and rejection sensitivity between family social class and social anxiety. The present study recruited 1400 undergraduates and adopted the MacArthur Scale of Subjective Social Class, Rejection Sensitivity Questionnaire, Liebwitz Social Anxiety Scale and self-report measures of psychosocial resources. Given previous studies have found optimism, mastery, self-esteem, and extraversion are most related to beneficial outcomes, psychosocial resources were measured by life orientation test-reversed, a measure of dispositional optimism; scale of sense of control, the Rosenberg self-esteem scale, the extraversion subscale of the Eysenck personality Inventory. We also collected the information about parents’ occupation, education level, and monthly family income, which were used as the indexes of objective social class. The results of bootstrap process analysis revealed that: (1) Family social class significantly predicted psychosocial resources (?=0.967，p < .001) and rejection sensitivity(?=-.145，p < .001) ; (2) When the mediate variables enter the equation, the effect of family social class on social anxiety turned out insignificant(?=-.487，p >.05) ; (3) Psychosocial resources significantly predicted rejection sensitivity(?=-.109，p < .001), and social anxiety(?=-.955，p < .001). Rejection sensitivity significantly predicted social anxiety (?=1.267，p < .001) ; (4) Bootstrap mediation analysis suggested that three mediate paths were all significant. The mediating effects were -0.924, -.134, and -0.184 respectively. Psychosocial resources and threat sensitivities partly mediated the effect of family social class on social anxiety. The mediation effect was 71.82% of total effect. In all, the current study suggested that family social class had a significant negative effect on social anxiety among Chinese undergraduates. Furthermore, psychosocial resources and rejection sensitivity had multiple mediating effects between family social class and social anxiety. Therefore, increasing psychosocial resources and reducing the rejection sensitivity might help social anxiety prevention and intervention of undergraduates from lower-class families.