This paper presented an EEAC-based （extended equal area criterion） credibility evaluation method of dynamic equivalent model. Firstly, the basic principles and methods of dynamic equivalent were introduced, and the effectiveness of dynamic equivalent model was discussed. Then, the power-angle stability margin and critical clearing time of prototype system and equivalent system were compared under different faults by using the quantitative theory of stability analysis based on EEAC, and the credibility index of equivalent system was defined. Finally, the stability quantitative index for test systems in different equivalent models was calculated in the IEEE 10-machine and 39-bus system and Fujian Power Grid by software Fastest. The simulation results show that the dynamic equivalent model based on dynamic similarity and buffer zone can better keep dynamic characteristic of the original system, and the transient stability analysis has better credibility.