Abstract: OBJECTIVE To explore the causes of nosocomial infections in elderly patients with mental diseases and put forward the prevention countermeasures so as to provide guidance for treatment and prevention of the nosocomial infections. METHODS A total of 660 elderly patients with mental diseases who were treated in the hospital from Jan 2012 to Dec 2014 were enrolled in the study, then the clinical data of the patients were investigated, the influencing factors for the nosocomial infections were analyzed, and the effective prevention measures were formulated according to the influencing factors. RESULTS Of the 660 patients, 89 (171 case-times ) had the nosocomial infections with the infection rate of 13.48%, the case-time infection rate 25.91%. The infection rate was highest (57.30%) in the patients with schizophrenia. The patients with respiratory tract infections accounted for 67.42%. The infection rate was 35.96% in the patients aged from 70 to 75 years old. The infection rate was more than 50.00% in the patients who were hospitalized for no less than 1 year. The prevalence rate was influenced by the temperature and was highest in summer, and the infection rate was as high as 46.07%. CONCLUSION There are a variety of influencing factors for the nosocomial infections in the elderly patients with mental diseases, and the corresponding prevention measures have been formulated based on the related factors.