Abstract: With the intensification of global climate change, extreme weather events will become more frequent, especially heatwaves, seriously affecting agroecosystems and human health. There have been many controversies about the definition of heatwave events, and understanding the spatial distribution characteristics of heatwave trends needs further improvement. Compared with definitions of absolute or relative temperature, this paper adopts a heatwave indicator that considers the daily temperature range and combines both absolute and relative temperature. The spatial distribution and temporal change characteristics of future heatwave events in China were evaluated based on the results of a multimodel ensemble of nine CMIP6 climate models under three different development scenarios: (1) SSP1-2.6, (2) SSP2-4.5, and (3) SSP5-8.5. Results show that (1) future heatwave events under the SSP1-2.6 scenario peaked around 2050 and then stabilized, while the frequency, days, and longest duration of heatwaves under the SSP2-4.5 scenario showed an increasing trend. The growth trend and severity of heatwaves under the SSP5-8.5 scenario are both the highest. (2) South China and Central China will face a greater risk of heatwave occurrence in the future. The frequency and intensity of heatwaves under the SSP5-8.5 scenario are about twice or more than those of SSP1-2.6, while those of SSP2-4.5 are about 1.5 times those of SSP1-2.6. (3) The occurrence of heatwaves of a larger scale in arid/semiarid regions in the west and arid regions in eastern Inner Mongolia, combined with the definition of heatwaves in this paper, predicts that nocturnal warming is an important feature of global warming. Results of the study help to understand the characteristics of future changes in the frequency and intensity of heatwaves in China under sustainable development and medium forcing scenarios and provide effective references for developing energy conservation and emission reduction programs for regional development.