This study attempted to investigate the mental health status of Beijing residents. Using Multiple-Item SRH Measurement Scale （SRHMS1.0），the investigation assessed the mental health status of Beijing residents. The study also considered the related social demographic variables，including sex，age，ethnicity，marital status，education level，income，occupation，etc. The 5196 questionnaires were sent out，and 5010 were effective，the rate of recovery was 96.4%. The results indicated that：for Beijing residents，the mean score for self-rated mental health and social health were 80.88 and 78.87 respectively；20.3% of the residents were in poor mental health status，and 22.5% of the residents were in poor social health status；for such groups like the old，the divorced & widowed，the unemployed，the temporary workers，the middle-aged，the high educated，the high & medium income population，the professional，their self-rated mental health status were relatively worse than other groups. The research also discussed the influence factors on the mental health of Beijing residents，including social demographic variables，personality characteristics，environment factors，cognitive & behavior factors，etc.Finally，from the perspective of social work，this research also provided some related suggestions for the service work towards mental health.