A method of identification of weak links of electric-gas integrated energy system based on time Petri net is proposed in order to effectively identify the weak links and prevent cascading major accidents. The Petri net is used to abstract modeling of the system, determine the associated region subsystem of the fault source, and construct the time Petri nets model based on the cascade fault path to describe the dynamic characteristics and time-sequence differences of the fault propagation of the electrical-gas system. The cascade hazard evaluation calculation is integrated into the operation of the Petri nets to find the key link to cause cascade failure. The simulation analysis of the electrical-gas coupling system composed of IEEE30 node and 25 node natural gas system verifies the effectiveness of the proposed method.