ObjectiveTo investigate the status and development trend of healthcareassociated infection(HAI) in a tertiary hospital, and provide a basis for formulating prevention and control measures. MethodsHAI data of clinical departments in a hospital from 2010 to 2012 were analyzed with trajectory model.ResultsAll clinical departments were divided into three groups according to development trend of HAI rate. The first group accounted for 80.7% of total departments, HAI rate of this group was low, and showed a decreased trend(slope=-0.45), the difference was significant (P=0.04); the second group accounted for 16.0%,HAI rate was higher than the first group and also showed declined trend(slope=-0.17),the difference was not significant (P=0.17); the third group only contained intensive care unit, HAI rate was far higher than other departments, and the development trend of HAI rate increased first and then declined.ConclusionTrajectory analysis model can be used to divide clinical departments into different groups, is convenient to understand the development trend of HAI of every hospital department, and take measures to control HAI according to the characteristics of HAI of different clinical departments.