Abstract: Power system fault diagnosis approach based on fuzzy Petri net in consideration of time sequence is proposed.By analyzing the characteristics of a fault diagnosis model,a fast modify method of the model when network topology structure changes is presented.Through full and reasonable using time sequence property of operation information of circuit breakers and protection,a correction algorithms is proposed in case of incomplete information of relay operations,and a better operation evaluation for relay protection can be completed.As an example,a 14-bus system is tested to verify the accuracy of diagnostic methods and the fastness of model updating method.In comparing with existing methods,the novel method proposed has better accuracy and higher speed,and can adapt to the network topology changes and in favor of large power system fault diagnosis.