Abstract: Objective: To study the risk factors for secondary caries in posterior teeth,and to provide ways of prevention.Methods: One thousand five hundred teeth with caries restoration were collected and 426 teeth which developed secondary caries were analyzed.Results: Secondary caries were obviously related to the filling time,material,position,oral hygiene status,the preparation of caves and so on(P<0.005).Conclusions: Improper materia time,position,oral hygiene status and the preparation of caves are the risk factors for secondary caries.