When globe-cone sealing has long storage or working requirement, it is necessary to consider the effect of stress relaxation on the globe-cone seal performance. Based on this, a finite element model of globe-cone sealing considering stress relaxation is established, and the law of the nut residual preload force and the contact stress between globe and cone is obtained with increasing creep time by this model. Then the calculating formulas of globe-cone seal leakage rate are presented by the leakage model which is presented by Roth considering stress relaxation effect, and the law of leakage rate is obtained with increasing creep time under different working parameters. The effect of stress relaxation on globe-cone seal performance is analyzed in the paper, which would be practical in the engineering design, and also improve the theory system and method about globe-cone seal performance analysis in a certain extent.