A numerical calculation model for airfoil dynamic stall numerical simulation was established by computational fluid dynamics method, and the influence of plunging motion on airfoil unsteady aerodynamic force was analyzed. The simulation results were compared to the pitching motion wind tunnel experimental data of NACA0012 airfoil, and the results of the model under mild stall and deep stall conditions were in good agreement with the experimental values, which verified the accuracy and feasibility of the numerical calculation model. The plunging motion of NACA23012 airfoil was equivalent to the pitching motion, the lift characteristics of airfoil under the two motion modes are very close, but the moment characteristics are obviously different. With the increase of amplitude of plunging motion and inflow Mach number, the difference of moment characteristics is further expanded. With the increase of amplitude of plunging motion, the damping effect of aerodynamic moment of pitching and plunging motions is obviously enhanced, with the increase of inflow Mach number, the damping effect is reduced, and the moment divergence occurs when the Mach number is 0.85.