Objective To observe the effect of the occupational therapy (OT) on people with mental disability in community of Beijing and analyze its related factors. Methods 180 mentally disabled persons from 15 disabled persons' centers (DPCs) in a district of Beijing were studied with a self-developed questionnaire. They were investigated twice with a 6-month interval, and the results were compared. Results 160 questionnaires were valid for analysis. The score of OT improved (P<0.05) in 103 (64.38%) respondents. The main factors related with the effectiveness of the OT included OT categories, age and vocational assessment. Conclusion OT is effective on people with mental disability in the DPCs, and could be improved in some aspects, such as regular vocational assessment.