According to the engineering characteristics of the reconstruction of existing buildings，the fuzzy analytic hierarchy process（FAHP） method is used to establish the risk assessment model for the reconstruction of existing buildings. The implementation of the model includes six steps： （1） collection and identification of construction risk factors；（2） establishment of judgment matrix； （3） weight calculation； （4） construction of membership function；（5）calculation of the degree of membership； （6）comprehensive operation of fuzzy weight. Finally，the proportions of risk factors in the reconstruction of existing buildings are obtained，and the safety levels of reconstruction are further determined. It is verified by an example that the model and the result of the example have satisfactory consistency. Therefore，the application of FAHP method in the risk assessment of the reconstruction of existing buildings is very effective and worth popularizing.