Objective To explore the role of social work in the three-level prevention system of community mental health. Methods A total of 100 patients with mental disorders registered in H District were selected and randomly divided into an intervention group and a control group,with 50 cases in each group.The control group received only routine mental disease prevention and treatment,the intervention group receiv the services of the three-level prevention system under the intervention of social work.The patients in the two groups were evaluated with positive and negative symptoms ,the medication compliance and patient rehospitalization rates before and after the intervention. Results After the intervention,the total score of negative and positive symptoms in the intervention group was lower than that in the control group,and the difference was statistically significant(t=--6.712,P<0.001).The medication compliance score in the intervention group was better than that in the control group,and the difference was statistically significant (χ²=6.444,P=0.040),and the rehospitalization rate in the intervention group was 4.08%,lower than 18.75% in the control group,the difference was statistically significant(χ²=5.020,P=0.025). Conclusion Using social work case,group and community methods to intervene in the three-level prevention system of mental health can effectively improve the medication compliance of patients,ameliorate patients' psychotic symptoms,and reduce the recurrence rate,thereby improving the effect of three-level prevention system of mental health.