Nozzle damping is an important factor affecting the unstable combustion of solid rocket motors. In this paper, numerical calculation methods and influencing factors of nozzle damping are systematically studied and summarized. Firstly, the advantages and disadvantages of two numerical calculation methods of nozzle damping, pulse decay method and steady-state decay method, are compared, including analysis of the calculation parameters. Then, the difference of two types of gas intake methods(end-burning and side-burning), and the influence of long tail nozzle on nozzle damping were simulated and discussed. Results show that the pulse decay method is easier to operate, but the steady-state decay method is more stable and accurate. Nozzle damping coefficient with side-burning is much higher than that with end-burning, which is mainly caused by the difference between numerical simulation conditions and actual conditions. Long tail nozzle will increase the nozzle damping with axial vibration but decrease with radial vibration. Finally, the effects of calculation parameters, geometric parameters and flow parameters on nozzle damping are summarized, in order to provide some reference for solid rocket motor nozzle design and suppression of unsteady combustion.