There are low stress areas of C-ring in the sealing process,and these areas are difficult to ensure the sealing reliability.In order to study the sealing characteristics of C-ring,it is necessary to analyze the effective contact stress and region.The C-ring with 318 mm outer diameter was selected as the research object.Using equivalent wall thickness instead of coil spring wire diameter,the equivalent model of C-ring was established.The rationality of the model was verified by compressive and resilient test.The effects of silver layer thickness,cladding layer thickness and equivalent thickness（spring wire diameter） on the sealing performance of C-ring were studied by finite element method.The results show that the effective contact width of the silver layer surface increases with the increase of the silver layer and cladding layer thickness,and the effective contact stress decreases with the increase of the silver layer and cladding layer thickness.The increase in equivalent wall thickness can simultaneously increase the effective contact width and effective contact stress.The structural parameters of C-ring were optimized by orthogonal experiment.The results show that the silver layer thickness and the wall thickness have significant influence on the effective contact stress and effective contact width.The optimal design parameters of silver layer thickness,coating thickness and spring wire diameter are 0.2 mm,0.5 mm and 3.1 mm,respectively.The leakage rate test result indicates that the optimized C-ring has better sealing performance.