Abstract: Up-righting of a ship floating upside-down is usually a complex operation. In this paper, it focuses on the mechanics analysis of the wrecked ship in still water. Firstly we calculate the stability of the ship in the inverted mode. Then a preliminary up-righting scheme is worked out. Besides that, we have a mechanics analysis of the up-righting procedure, and use floating cranes for up-righting the ship and,ground tackles for stabilizing in the meantime. In this research, we compute all hydrostatic properties of the ship and lifting force during the course of up-righting works. We use application program MATLAB to realize numerical simulation for that works, and analyze the calculated result.