This study internalized social capital on the basis of traditional study of the influence of economic factors on self-efficacy, and studied the relationship among the family socio-economic status, social capital and self-efficacy. Based on the theoretical analysis, with first-hand data collection and using multiple regression models, the paper studied the intermediate effect of social capital in the relationship between the socioeconomic status and self-efficacy. We draw on the following conclusions: (1) The family socio-economic status as well as all its dimensions (father’s degree of education, mother’s degree of education, the total annual income of the family, father’s occupation, mother’s occupation) is significantly positively related to social capital and all the dimensions of its proxy variable (peer support, kinship support and general support of others); (2) There is a significant positive correlation between the family socio-economic status as well as all its dimensions and self-efficacy; the socio-economic status, with its dimensions, is the predictive variable of self-efficacy; (3) Social capital, with dimensions of its proxy variable, is positively correlated with self-efficacy and has predictive effect on self-efficacy (4) Social capital plays a significant intermediate role between socio-economic status and self-efficacy, and the mediating effect size is about 51.75%.