Objective To explore the influencing factors of district government investment in mental health service in Shanghai, and provide referrences for financing mechanism of mental health service. Methods The data of government investment in mental health service, populations and economic status, prevalences of mental diseases and status of mental health service supply in 19 districts of Shanghai from 2004 to 2008 were investigated, and the influencing factors of government investment in mental health service were analysed with econometric model. Results The district government investment in mental health service of Shanghai was related to fiscal revenue per capital, gross domestic product per capital, ratios of patients with mental diseases to total populations, accident rates of patients with mental diseases and numbers of medical staff in mental health centers (P<0.05), and accident rate of patients with mental diseases was the most important influencing factor （r＝0.715, P＝0.000）. Conclusion District government in Shanghai should establish a rational financing mechanism in line with the economic status, and allocate a proper budget for mental health service from total government expenditure.