Abstract: Extreme sea conditions pose a significant threat to the safety of offshore structures. Generally, extreme value theory is used to predict extreme sea conditions under future climate change within a certain time range for evaluating the response of structures under extreme sea surface winds, currents, and waves. The extreme values obtained through extreme value analysis will vary due to differences in extreme value samples, probability distribution functions, and parameter estimation methods, and the differences in extreme values will further affect the safety and economy of the structure. Therefore, using hydrological simulation time series data from a proposed wind turbine location in the Wenzhou Sea Area of Zhejiang Province, spanning 43 years from 1979 to 2021, to explore the sensitivity of once-in-50-year wave height to different extreme value samples, probability distribution functions, and parameter estimation methods. The results indicate that, under the condition of good fitting performance, the sampling method and the probability distribution function have a significant impact on the once-in-50-year wave height, while the parameter estimation method has a relatively small impact on once-in-50-year wave height compared to the other two factors. To ensure the safety margin of the structure, it is recommended to prioritize analyzing the sensitivity of extreme wave heights. In this case, the Pearson III distribution and annual sampling method demonstrated high stability and low sensitivity in extreme value estimation. The research results can provide a reliable reference for the accurate calculation of extreme wave heights.