A fast algorithm for calculating short-circuit current based on Thevenins theorem and compensation method is presented.With compensation method，compensation current is introduced in the algorithm into the fault ports for modeling the influence of node short-circuit faults on original network.It can solve the state variable of post-fault network by using nodal admittance matrix of pre-fault network without modification，then solution of the whole network is obtained.Compared with general algorithm，the algorithm proposed can not only compute various short-circuit faults，but also save time for solving post-fault admittance matrix.With faster computing speed and higher precision，the algorithm can better meet the demand of the real-time calculation of short-circuit current.