Abstract: According to the result of safety review and inspection on Chinese existing and under construction nuclear power plants post Fukushima accident, it is found that there are some weak points in the CPR1000 nuclear power units in the accident of SSE（safety shutdown earthquake） with long term SBO（station black out） and LUHS（loss of ultimate heat sink）.Due to the lack of emergency cooling systems, the spent fuel pool could be damaged by these accidents. So it is necessary to improve its safety feature for CPR1000 units. From the point view of defense in depth, assumed the same kind of Fukushima accident, the possible accidents combination is established on the basis of confidential methodology. For these accidents, the safety functions or strategy for prevention or mitigation are given. And the new modification solutions, like spent fuel pool monitoring, make up and steam exhausting, are raised for CPR1000 units under different construction situation. They are proved to be feasible and available for these extreme accidents and the CPR1000’s safety and reliability are improved largely.