ObjectiveTo investigate the relationship between occurrence of healthcareassociated infection (HAI)  and seasonal change， so as to  provide the basis for seasonal HAI prevention and control.MethodsThe occurrence of HAI among inpatients in a hospital between 2010 and 2013 was analyzed retrospectively.ResultsOf 303 371 patients, 10 376  developed 12 919 cases of HAI, the incidence of HAI was 3.42%， infection case incidence was 4.26%. The highest incidence of HAI occurred in the fourth quarter（3.76%）and lowest in the second quarter （3.20%）(P ＜0.01); the main HAI site was lower respiratory tract (39.79%), followed by upper respiratory tract (13.17%), blood stream (10.39%), surgical site (8.60%)， and urinary tract (7.91%). Patients in the following departments were with HAI rates of ＞5%: intensive care unit（ICU, 24.61%）,hematology（17.47%）,rehabilitation（13.16%）,neurosurgery（9.27%）, infectious diseases （9.17%）, cardiothoracic surgery（7.67%）, and hepatobiliary surgery（5.13%）,the main HAI sites in patients in ICU, department of neurosurgery were lower respiratory tract, blood stream, and urinary tract.ConclusionThe occurrence of HAI is closely related with  seasonal change, appropriate control measures should be taken according to  seasonal change and sites of high HAI rates, so as to reduce the occurrence of HAI.