Abstract: In this paper the investigations on the delamination damage of fiber-reinforced composite laminated plates have been done by both experiments and three dimensional finite element analysis.The obtained results show that the delamination of these laminates always occurs on A/90 interfaces where both interlaminar shear stresses and interlaminar normal stress are much bigger. It can also be seen that the critical strain energy release rates G_ⅠC and G_ⅡC vary with the stacking angle θ for different A/90 interfaces of laminates.A delamination criterion of mixed mode strain energy release rate has been improved for its applications.The experimental results obtained show that this improvment is effective.