In view of the erection problem of the offshore launching platform of the vehicle rocket, the offshore launching platform motion model was established by comprehensively using the ship’〖KG-*2〗s seakeeping and multibody dynamics theory. The erection load variation obtained by the analytical method was compared with the dynamic simulation results of the 0level sea state, and the correctness of the erection mechanics model was verified. In order to simulate the erection problem in complex sea conditions, the dynamics simulation of the platform’〖KG-*2〗s heave, pitch and roll coupling motion was carried out by using the platform motion function condition obtained from the ship’〖KG-*2〗s sea wave resistance theory. The law of load variation of erecting device under different sea conditions and different erection directions was obtained. The results provide some reference for the antiwind wave design of erection system and the design of hydraulic and control system.