As an important part of social mentality，social trust not only has important significance for individual health and happiness，but also a barometer of social healthy development and integration. This study investigates the current situation and the source of social trust by using large-scale national sample data. The results of this study are as follows：（1）In terms of the overall situation of social trust，acquaintance relationship trust is the main model of social trust in contemporary China，and social trust model based on professional group and stranger has not been established；（2）In terms of the specific characteristics of social trust，there shows a certain group differences；（3）In terms of the source of social trust，the sense of security and fairness are closely related to social trust，but the influence of residence mobility on social trust is weaker.