The fatigue residual stiffness distribution of fiber-reinforced polymer composites (FRP) is one of the basic data for fatigue reliability assessment of FRP structures. In this paper, a residual stiffness probability model is proposed. The median curve of the model is a combination of an exponential function and a linear function，and the residual stiffness under a given normalized life obeys a normal distribution. The static and fatigue tests of the two laminates of glass fiber and carbon fiber composite specimens are completed, and the residual stiffness curves of different materials under different loads are obtained. Research result shows that the model proposed in this paper can better describe the test results.