Based on the tornado survey data in the three longitude and latitude regions around the Yuping Nuclear Power Plant site from 1950 to 2021, the tornado grade is assessed by using the Fujita scale method. The design basis tornado parameters and grade in the assessment area are calculated according to Extreme Meteorological Events for the Selection of the Nuclear Power Plant Site (HAD101/10). The results show that the recommended maximum wind speed of the design reference tornado around the Yuping Nuclear Power Plant site is 63.9m/s (corresponding probability value is 10-7), the total pressure drop is 29.5 hPa, the pressure drop rate is 7.1 hPa/s, the maximum rotating wind speed is 51.8 m/s, the maximum translation speed is 12.1 m/s, and the design reference grade is F2. The calculation results provide important theoretical reference for project design and construction.