Risk assessment for power transformer is an important means to guide the condition based maintenance of transformer and enhance the reliability of power system operation, but also to strengthen the power transformer to provide an important basis for quality control. In this paper, an index system for comprehensive evaluation of transformer is put forward and a risk assessment model for power transformer based on fuzzy synthetic evaluation is built, which based on the quality problems of large power transformer statistics of State Grid Corporation of China(SGCC) in 2012 and combined with multilayer and multi-factor features of the transformer life cycle management process. The assessment example analysis shows that the method can effectively estimate the risk of each stage for the life cycle management of power transformer and provide feasible decision basis for the risk management and maintenance decision of transformer.