It is conductive to improve the power supply capacity of power grid in the southern part of Suzhou based on unified power flow Controller (UPFC).However,the integration of UPFC has an impact on the reliability,selectivity and sensitivity of transmission line protection.In this paper,the fault equivalent model of 500 kV UPFC in Southern Suzhou is built combined with the control and protection logic after line fault,then the influence on distance protection action is analyzed,as well as the coping strategies are proposed.