Abstract: The overall structure of the reactor protection system of CPR1000 nuclear power plant was studied in this paper, and its defense in depth was analyzed. On this basis, the software common cause failure and AP1000 nuclear power plant’s handling technique of diversity actuation system (DAS) were introduced, and CPR1000 nuclear power plant’s DAS basic functional requirement and the method of the realization of the simulation were mainly studied. There was an example of the transient accident related to the steam generator tube rupture in the main feed water system in the containment. The DAS function verification was proved in the case of common cause failure in the protection system, and the whole process was analyzed in detail as well. All of these confirmed its feature set can carry the plant to the safe state and alleviate the consequence of the accident effectively.