In the process of oil and gas development, semi-submersible platforms operate relocation between wells by retracting and releasing mooring chains. In this paper, a fast well relocating optimization method of semi-submersible platform based on greedy algorithm was proposed in view of the traditional method that cannot obtain relocation strategy quickly. Three sets of relocation operations were selected in this study, an optimization analysis of relocation strategy was carried out for windlasses normal operation and windlasses failure operation. The results show that under normal operation, the optimized strategy has a significant improvement in terms of optimization effect and calculation cost compared with the original strategy and the best strategy. Under windlasses failure operation, it shows that the feasibility of relocation is closely related to the distance and direction of the relocation operation. A comparison of relocation strategy was made between the normal operation and the windlasses failure operation, it was found that the retracted length of the mooring chains and the number of operating steps increased under windlasses failure operation, and the stability keeps changing with different working conditions.