OBJECTIVE To sdudy the characteristics of nosocomial infections in psychiatric hospital and to take the corresponding prevention measures to control. METHODS The epidemiological characteristics of nosocomial infections occurred in the patients treated in psychiatry department of our hospital from Jan 2003 to Dec 2006 were retrospectively analyzed. RESULTS Of all 5741 patients, 367 cases were definitely diagnosed as nosocomial infection. The incidence was 6.39%, with a decreasing trend. Among these infections, upper respiratory tract infections accounted for 52.78%, lower respiratory tract infections for 13.26%, and gastrointestinal infections for 11.14%. Other sites infections were rare(11.41%). The respiratory tract infection occurred all the year around, especially in the winter, other sites (included skin) infections mainly occurred in the first and the third quarters. The gastrointestinal infection reached its highest in the summer. CONCLUSIONS The nosocomial infection in psychiatric hospital has some characteristics and regularities. These are related to the particularity of the patients, the long stay in hospital, and poor self-care ability. Accordingly, we can take reasonable measures to prevent and control nosocomial infection.