The weight difference between different feature parameters is not considered in the traditional process of constructing health indicator. The study proposes a dynamic degradation distance to overcome the above problem and is used in the construction of health indicator of gun anti-recoil device. Firstly, the unique feature parameters Xmax, Vmax, Umax, Uend and common feature parameters of the gun anti-recoil device signal were extracted to form a vector group of feature parameters, and the feature selection is completed by the volatility index and box plot. Then the dynamic degradation distance is used to address the difference between the standard state and other states of the gun anti-recoil device. Finally, based on the dynamic degradation distance and exponential function, the health indicator of gun anti-recoil device is constructed. The simulation results show that the health indicator constructed in this study has the best performance, and the monotonicity is 0.0614 and 0.7253 higher than that of the method proposed in the references, which indicates that the health indicator constructed in this study can effectively evaluate the degradation state of the gun anti-recoil device.