Abstract: Residual stress in viscoelastic resin matrix composite laminates at room temperature can keep varying during a long period of time. The characteristic can be reflected by the curvature variation of unsymmetrical laminates. A curvature variation test of unsymmetrical laminate was conducted and the test results indicate that the curvature and residual stress can finally tend to a stable state. Based on the test results, a revised ply stiffness matrix corresponding to the final stable state is deduced by means of a micromechanics model and the calculation method appropriate for the large deformation of composite laminates. The revised stiffness matrix can be used to predict the final stable state of the residual stress and deformation of composite laminates with different stacking sequences, and then determine the variation scope of residual stress. Tests of different laminates for verifying the effect of revised stiffness matrix were also conducted and the test results quite agree with the prediction.