Abstract: To study the variation of the interface shear stiffness of fiber reinforced plastic (FRP) bar bolt and grout, several groups of test data for the shear stiffness are analyzed and fitted into curves, and the curves of the interface shear stiffness of FRP bar anchor bolt against the shear displacement are in exponential variation. Combined with the damage mechanics theory, based on the equivalent strain assumption, the shear stress and shear displacement models with Weibull and power function distributions are established, respectively. It is shown that the model established based on the fitting law and the Weibull probability distribution is in good agreement with the experimental data. The degradation of the interface shear stiffness of FRP bar bolt and grout is closely related with the shear position, and based on this, the force transfer analysis of the bolt is carried out.