Abstract: To verify the safety of China Experimental Fast Reactor (CEFR) under one main pump trip state, a test is going to be performed on CEFR. In order to ensure the safety of reactor, the system code OASIS was applied to simulate the test and analyze the risk existed. The calculation results show that the operation in accordance with the test procedure will not pose a threat to the safety of reactor and the most possible risk derives from the flow rate mismatch problem between main heat transfer systems, which may cause a significant thermal shock to components.