Abstract: An improved degradation model is proposed to understand the operation conditions of wind turbines. Firstly,the degradation degree of each parameter in the hierarchical structure of wind turbine is calculated. Secondly,the weights of each state parameter and the parameter matrix are determined by an integrated method and the ridge type membership function respectively. Finally,the fuzzy comprehensive evaluation method and color images are used to evaluate and display the operating status of wind turbines. Results shows that the proposed method can detect the abnormal bearing at the non-drive end of wind turbine generator before the SCADA system,and the number of false alarms is less.