The Hongyanhe nuclear power plant is located in Liaodong Bay,northern China,which is often invaded and impacted by tropical cyclones.Observations and statistics show that the tropical cyclones landing in Liaoning can't be ignored because their strength can reach to ty phoon level.The tropical cyclones impacting on Hongyanhe mostly occur in July and August.The tropical cyclone which has a route like moving to north-west after entering the Bohai Sea or north across the Shandong Peninsula landing in the Liaodong Peninsula has the strongest impact on Hongyanhe area.The maximum wind speed of tropical cyclone impacting Hongyanhe achieves 25-33m/s and the extreme velocity reaches above 40m/s in the past 56 years since 1949.Using theory of probability and gradient wind formula to design Hongyanhe nuclear power plant area,the possibly maximum intensity parameters of tropical cyclone are: the minimum pressure at 961 hPa and the maximum wind speed at 35.4m/s happening once in a century,the lowest possible pressure at 939hPa,the maximum wind speed at 42.2m/s and the extreme wind speed at 54.9m/s happening once in a millennium.