To research the effect of the structural parameters of builtin spring coil in the metal Cring of nuclear power plant on the sealing performance of Cring,threedimensional elasticplastic finite element analysis model of Cring was built,and the reliability of the theoretical model was verified by the experimental study.The effects of the structural parameters of spring (including spring pitch,wire diameter and medium diameter) on the mechanical behavior and sealing performance were discussed.The results show that for the millions of kilowatt nuclear reactor pressure vessel with metal Cring,the spring pitch,wire diameter and medium diameter respectively within the scope of 1.9~2.0 mm,1.7~1.8 mm and 8.3~10.7 mm can ensures that Cring has good sealing performance.Tightness experiment verifies the accuracy of the results.After compression deformation,the sealing surface of Cring is flat,no crack,as well as the local loss or peeling phenomenon.So the sealing performance of metal Cring meets the engineering requirements.