Abstract: The residual strength of glass fiber/epoxy composites after immersion aging in water was studied. The water absorption property of resin and the tensile properties of resin, fiber and composites were tested after and before aging in water. Based on the test, the residual strength of the glass fiber/epoxy composites after water immersion aging was calculated using a bridging model. The numerical results indicate that the theoretical values calculated by the method are well fitted with the test results. The results show that the model could be used to accurately predict the progressing damage regulation and the strength under the condition of low water absorption ratio. When the main bearing layers damage are controlled by fiber, the descending of fiber tensile strength caused by water immersion directly results in the descending of the composites maximum tensile strength. The major factor on the residual strength of composites is resin harden and tensile strength decreasing caused by water immersion to the layers controlled by resin. The effect of the low water absorption ratio on the strength of the interface of fiber and resin is finite.