The selection of flange and bolt materials is an important factor to affect the sealing performance of bolted flange joints,especially with creep under high temperature service.Two sorts of flange joints are selected,one is the creep rate of flange material greater than bolt material,and the other is on the contrary.By analyzing the heat transfer,the thermal structure coupling and the high temperature creep,the sealing performances of the flange joints were studied.The results show that both bolt creep and flange creep can cause bolt stress redistribution,and the accumulation of bolt creep will lead to more uniform bolt cross-section stress.But the accumulation of flange creep will reduce the flange stiffness,resulting in the increase of deflection angle and then causing the increasing difference of internal and external forces of bolts.The larger the flange creep rate,the faster the overall flange stiffness decreases and the shorter the flange service life.Therefore,when choosing the materials of bolt flange joint in high temperature service,the creep rate of flange materials should not be too large,and their creep resistance should be better than that of bolt materials.