Abstract: The passive autocatalytic recombiners,pressurizer depressurization function extension （prevention high pressure melt core） and containment pressure relief and filter releasing system are used as the prevention and mitigation measures of severe accidents to prevent and mitigate the consequences of severe accidents in CPR100 nuclear power plant,to ensure the integrity of the containment of CPR1000 nuclear power plant under severe accidents and thus to protect the surrounding residents from the dangers of nuclear radiation. Based on the spectrum analysis of severe incidents,the LBLOCA + loss of safety injection pumps,station blackout,loss of all feed water +anticipated transient without scram and MSLB + loss of containment spray are selected as the important severe accident sequence.