The work aims to study the approximate analysis on drop impact response of nonlinear system with typical cubic nonlinear system as the research object. The conservative buffer packing system with complex nonlinear terms was studied. Taking a cubic nonlinear system as an example, the first order approximate solution of the drop impact response was obtained by solving the motion equation with homotopic perturbation method, and the first order approximate solution was modified by energy method. Based on the expression of the maximum acceleration response, the damage boundary surface of the nonlinear system was obtained and the damage evaluation of the system was carried out. The maximum displacement response and the maximum acceleration response of the modified first order approximate solution were closer to the values of Runge Kutta method. With the increase of product brittleness value, the damage boundary curve moved up gradually and the system was more secure. The application of homotopic perturbation method can provide convenience for the subsequent nonlinear drop impact analysis.