China is in a period of social transformation and social change, and social risk is increasing. One important characterization is that group events frequently occur. It hints that people do not accept public policy. If formulation and implementation of public policy does not fully consider public acceptability, it is likely to constitute a new social risk, threatening social stability. Therefore, how to effectively improve public acceptance of public policy has become a major problem that should be solved in our country. Studies have found that procedural justice, uncertainty, trust all affect acceptance of public policy, but previous studies are more qualitative analysis, exactly how these variables influence acceptance of public policy, and what is the internal mechanism are lack of further empirical research. The present research integrated social exchange theory, fairness heuristic theory and system justification theory,establishing a hypothesis model of acceptance of public policy with the impact of procedural justice and uncertainty, as well as the mediating effect of cognitive trust and affective trust. Since Thibaut and Walker (1975) introduced the concept of procedural justice from the legal field, procedural justice has become the research focus in organizational justice field. Procedural justice affects people’s attitudes and behaviors, and trust is an important mediating variable in the procedural justice effect.With the deepening of the research,scholars start to explore affective trust and cognitive trust’s mediating role respectively. In addition, according to system justification theory, when faced with uncertainty, people will lack a sense of control. To compensate people's basic needs - a sense of control, people will tend to think that the system can control things, reducing uncertainty. People will regard the system as increasingly legitimate, and thus increase confidence in the authority. We randomly selected 510 Beijing residents, and used the questionnaire survey research method to explore the hypothetical model. All the data was analyzed with the software AMOS 17.0. Bootstrap method was used to analyze the mediating roles of affective trust and cognitive trust. The results indicated that procedural justice was positively related to the acceptance of public policy, uncertainty was negatively related to the acceptance of public policy. Affective trust mediated the relationship between procedural justice and acceptance of public policy, and the influence of affective trust between uncertainty and acceptance of public policy was suppressing effect. There was no significant mediating effect of cognitive trust. These findings suggest that when the public policy formulation process is fair, people will have high affective trust in government, and as a result they are willing to accept the public policy. The influence of affective trust between uncertainty and acceptance of public policy was suppressing effect. It indicates that the study fails to take into account all of the mechanism. There may be other mediating effect between uncertainty and acceptance of public policy. Anxiety is likely to be an important mediating variable, future research can further explore the other specific mechanisms.