The invention provides a simulation method for a self-supporting body of an amphibious vehicle. Different objective functions are defined through a typical method, and the self-supporting body is worked out through an optimization process of an algorithm. The simulation method comprises four necessary design procedures of setting of multiple targets in structure topological optimization, determination of an evaluation method of the multiple targets, determination of a simulation method of structure topological optimization, vehicle body structure design based on the optimization result and the like, and the optimal topology of a product is determined based on the result of topological optimization for the targets. The simulation method greatly guarantees that the design size and shape of the amphibious vehicle body structure are carried out under a material distribution optimal initial topological mode, can greatly improve the material utilization rate, determines the optimal layout of a main supporting structural part of the vehicle body, largely saves the design time, obviously improves the structure optimization level of the high-speed amphibious vehicle, and further guarantees a rapid, reliable and stable work state of the amphibious vehicle.