Abstract: Fault modeling is crucial for power system simulation. There is no fast,accurate or complete method to model some common type faults（ such as N-1 fault,N-2 fault）,which troubles the system analysts. Firstly,two factors considering in fault modeling are analyzed,that is,fault route and fault action sequence,in which fault route is the difficulty of fault modeling.Secondly,a power system fault modeling method based on graph calculation is proposed with the consideration of the characteristics of power system data structure. Finally,a case of real power system is demonstrated to verify the availability of the proposed method. In future,the proposed method can be a theoretic foundation and practical tool for both on-line and off-line power system simulation.