Abstract: Based on the historical daily maximum temperature data measured by CN₀5.1 from 1970 to 2014, the daily maximum temperature data of the CMIP6 from 1970 to 2100, and the measured growth period data of spring and summer maize in Shanxi from 2000 to 2014, the maximum temperature data of CMIP6 were downscaled and corrected, and the corrected maximum temperature data was obtained through the method of Bayesian model averaging. Based on the corrected meteorological data, the heat damage of maize in Shanxi in the past and future periods were evaluated. The results showed that: (1) R² were increased by 5.4%~21.0% and RMSE were reduced by 27.8%~79.7% through downscaling correction, which effectively reduced the system errors, and simulation errors were reduced through the method of Bayesian model averaging, and ensured the reliability of assessment results in heat damage. (2) In the historical period, the high incidence area of heat damage of spring maize was mainly located in the west of Lvliang Mountain and the south of Jincheng in the southeast of Shanxi. The values of Heat degree days (HDD) were generally less than 50 ℃·d, and showed a decreasing trend at the fastest rate of 34.3 ℃·d/10 a. The high incidence area of heat damage of summer maize was mainly located in Linyun Basin. The values of HDD were generally range from 50 ℃·d to 90 ℃·d, which increased in the south at a rate of 0 ℃·d/10 a to 13.6 ℃·d/10 a and declined in the north at a rate of -12.8 ℃·d/10 a to 0 ℃·d/10 a. (3) The high risk area of heat damage of maize in the future is consistent with the area with the high values of HDD in the historical period. Besides, except SSP1-2.6, HDD of maize in Shanxi showed an overall increasing trend with time and radiation intensity under the other three model scenarios. HDD of maize reached the maximum value in the last 20 years of the 21st century under the scenario of SSP5-8.5. The study will be of great significance to scientifically addressing climate change and ensuring food security by taking advantage of opportunities and avoiding risks.