Abstract: In recent years, the increase of strong typhoon frequency has posed a serious threat to the safety of the northern coast of Hangzhou Bay. It is necessary to improve the protection ability of seawalls and investigate the combination of return periods of hydraulic elements. Based on the numerical model of astronomical tide, storm surge and typhoon wave, we simulated the tide level and wave process generated by historical typhoons landing along the real route and assumed typhoons landing along the assumed route, and constructed a sample of tide level and wave height in front of Jiaxing seawall of the north coast of Hangzhou Bay. The results show that the majority of combinations of tide levels and corresponding wave heights caused by the historical typhoon are less than the combination of tide levels once-in-10-year and wave heights of the same frequency. There is only one above the once-in-10-year among the highest storm tidal levels during the landing of historical typhoons. The combination of return periods shows a combination of “high tide and low wave” return period. During the landing of the designed typhoon on the predicted path, according to the combination of hourly tide level and its corresponding wave height, when the tide level of Jiaxing seawall in Hangzhou Bay is once in 100 to 300 years, it will appear to have three kinds of phenomena about combination of returns: “equal tide and wave”, “low tide and high wave” and “high tide and low wave”. There will be two phenomena of “equal tide and wave” and “high tide and low wave” in the middle section of the seawall. In the combination of the highest tide level and maximum significant wave height in the typhoon process in front of the seawall, when the tide level return period is once in 100 to 300 years, only the phenomena of “high tide and low wave” and “equal tide and wave” appear. Therefore, the tidal level design standard for seawalls is once in 100 to 300 years, and the wave design standard should not be lower than the tide-proof standard.