通过对某海上移动式钻井平台进行的有限元法强度分析，找到了平台发生局部损坏的原因，由分析结果发现，在极端工况条件下，对该平台悬臂梁的改造导致弯矩剧增，使局部应力超过许用应力而造成损坏。通过补强设计，可以使其完全满足有关安全作业的要求，实验结果与计算结果吻合良好。 Through the strength analysis of finite element method for a offshore mobile drilling platform, the reason of local damage to the platform was found out. According to the analysis results, it is found that under extreme working conditions, the modification of the platform cantilever caused the sharp increase of bending moment, So that the local stress exceeds the allowable stress caused damage. Through the reinforcement design, it can fully meet the requirements of the safe operation, the experimental results are in good agreement with the calculated results.