OBJECTIVE To find out some risk factors of the aged mental patients′ nosocomial infection and supply theoryetical basis for the control measures of nosocomial infection.METHODS By using the target detecction, the nosocomial infection and the risk factors in the senile psychiatry department were investigated.RESULTS There were 878 cases of nosocomial infection.From them 48 cases were with nosocomial infection.The infection rate was 5.5%.The long stay in hospital,the aged and the complication of underlying diseases were the important risk factors.CONCLUSIONS There are many risk factors of nosocomial infection in the senile psychiatry department.Take measures in advance will effectively decrease the nosocomial infection.