Aiming at the problems of safety and attitude stability in the process of air separation of the internal load, the dynamic nested mesh combined with penalty function is applied to simulate the load separation process under the consideration of adapter collision in this paper. Compared with previous studies, this method transforms the aerodynamic characteristics of separation process from discrete steady-state calculation to continuous transient calculation and the calculation of adaptor collision is transformed from feature point method to node-surface method and the coupling solution of unsteady flow field and multi-body collision is realized, which has better fidelity. In this paper, the accuracy of the numerical method is verified by comparing it with the test of standard model in the wind tunnel laboratory of Arnolds Engineering Development Center of US Air Force. Then, the simulation model of load exit system is established and the influence of initial velocity and initial angle of attacks on the process of load exit under the action of towing parachute is analyzed. The results show that the load can safely and stably exit the cabin under standard working conditions; The lower the initial speed, the smoother the separation process, the lower the compression degree of the adapter, when the Mach number is 0.5, the minimum distance between the vehicle and the load increases by 1mm compared with that when the Mach number is 0.8. The larger initial angle of attacks has an adverse effect on the safety and stability of the separation. When the Angle of attack is 15°, the adapter friction is 2.67 times that when the Angle of attack is 5°. The method is suitable for the numerical simulation of the load removal system using the adapter as the safety protection measure, and the conclusion can provide some reference for the study of the separation process of the load removal system.