A new identification algorithm of power flow transferring for multi-branch removal event based on analysis of self and mutual transferring of power flow is proposed in this paper.When excision of many lines happens,refraction and reflection process of flow transferring is analyzed. The improved Floyd algorithm is used to determine the power flow routing set by path search. Based on the DC power flow method,the calculation of line tripping distribution factors is deduced,and the key branch set is formed by calculating the danger index of power flow transferring.Considerable improvements of the shortest path search and determination of generalized power flow transferring critical area are put forward,which are suitable for the effective identification of multi-branch removal.The simulation results of IEEE39 node system verified the effectiveness of the proposed algorithm.