When the flange joint works in a high temperature environment,the creep relaxation of each part of the joint is intensified.However,the creep relaxation of gaskets is mostly not considered in the study of flange joints.The creep relaxation performance test of metal-graphite spiral wound gaskets at different temperatures and different initial sealing specific pressures was carried out.By fitting the experimental results,the calculation formula for the creep relaxation performance of the gasket was obtained,and by substituting into the flange joint deformation coordination equation,the change of bolt force with time in 2 years of joint creep was obtained by calculation.The finite element model of the flange joint was established by ANSYS software the relaxation of the bolt force caused by the creep of different parts for 2 years was calculated.The theoretical calculation results are similar to the finite element calculation results,which indicates that the established theoretical model can be used for evaluating the joint bolt force relaxation.The research results indicate that when the initial sealing pressure is the same,the higher the temperature,the greater the creep deformation of the gasket.When the temperature is the same,the larger the initial sealing pressure,the greater the creep deformation of the gasket.The creep of gaskets has a significant impact on flange joints,and in some cases,only gasket creep can reduce bolt force by 40%.Therefore,the effect of gasket creep on flange joints cannot be ignored.