Hainan Island is in an area affected by tropical marine monsoon. Typhoons are frequent, often accompanied by strong winds, extreme waves, and rainstorms. The driving wind field is a reconstructed wind field, which is a combination of the Jelesnianski typhoon model and the ERA5 wind field, to drive the SWAN model and to obtain hourly wind and wave data for 20 years (2003–2022) of Hainan Island. Through comparison, this study found that the P-III distribution is more appropriate for calculating wind and wave extremes in this sea area. It was found that the maximum wind speeds and wave heights mainly occur on the northeast side of Hainan Island and the southwest side of the Xisha Islands. The maximum wind speed with a 50-year return period reaches 55 m/s, and the maximum wave height with a 50-year return period reaches 13 m.