Abstract: The offshore wind power industry is rapidly developing, and the single unit capacity of offshore wind turbines is increasing gradually. In response to the large diameter monopile foundation of offshore wind farms, the changes of local erosion depth around the pile foundation affect the frequency of the pile foundation and the cumulative fatigue damage value of the pile foundation throughout its entire life cycle. Reasonable calculation of the local erosion depth of the pile foundation and appropriate selection of erosion protection measures by considering project requirements are one of the key paths to effectively improve engineering design optimization. By comparing commonly used formulas for calculating local erosion of pile foundations and considering the influence of wave current joint action, an improved empirical formula is determined. Based on existing research results and compared to the currently available measures for erosion protection of offshore pile foundations , passive protection is more suitable for erosion protection of single pile foundations in offshore wind farms, and its protection effect is better. Finally, by comparing and analyzing the changes in fatigue damage of pile foundations under different erosion depths, combined with research on erosion protection measures, summarized the design optimization ideas considering the impact of erosion protection on the fatigue of large diameter monopile foundations .