The integration of wind power will affect the stability of the power system as well as the identification of critical lines in the power system. Considering the uncertainty of wind power output, segmentation discretization method is adapted to construct wind power fluctuation prediction scenarios and the influence of wind power access on power systems. The overload of the line is an important cause of the fault of power system. In this paper, the line load rate is taken as the research object to improve the power flow entropy. On this basis, combined with the trend of the line, the synthetic power flow index is used to rank the importance of the line, so as to identify the key lines of the power system. Finally, simulation on the critical lines identification of IEEE 39-bus system validates the validity and effectiveness of the proposed method. This work is supported by Key Program of National Natural Science Foundation of China (No. 51537010) and Collective Enterprises Science and Technology Project of State Grid Zhejiang Electric Power Company:Whole-Process Risk Assessment and Application of ‘Prevention-Check-Emergency’ Management and Control.