Compound heatwave events are heatwaves that occur simultaneously during the day and at night， which not only threaten human health but also impede sustainable socio-economic and ecosystem development. In recent years，the frequency of compound heatwave events in the Sichuan-Chongqing（SC）region has in‐ creased significantly，and an advanced understanding of the plausible factors of compound heatwave variations over the SC region is of great importance for a better understanding of their impacts. Based on observational and reanalysis data，the relationship between the summer compound heat wave frequency（HWF）in SC and the anomalous atmospheric heat source（AHS）over the Qinghai-Xizang（Tibetan）Plateau（QXP）is statistically analyzed in the present study. Then，this study evaluates the performance of 28 climate models from the Coupled Model Intercomparison Project Phase 6（CMIP6）in simulating the relationship between the SC HWF and the QXP AHS of 1985-2014 and explores the key factors causing the differences in the simulation capability among the models. The results show that both the climate mean and the standard deviation of the HWF have relatively large values in the eastern SC，where the HWF variability shows a significant negative correlation with the summer AHS over the southeastern QXP. When the AHS over the southeastern QXP is weaker in summer，an anomalous anticyclone is present over the eastern SC，leading to an anomalous downward motion. This anomalous descent induces cloud cover and surface shortwave changes，leading to the formation of heatwave events over the eastern SC. Most CMIP6 models can essentially simulate the spatial distribution characteristics of the observed climate states of the summer HWF in the SC region and the summer AHS in the QXP. However，the models perform better in simulating the standard deviation of the AHS over the QXP than in simulating the HWF in the SC regions. There are significant differences in the simulated relationship between the SC HWF and the QXP AHS between different models. This is mainly due to the different abilities of the models to simulate the anomalous vertical motions over the SC regions corresponding to the anomalous summer AHS over the QXP. Further analysis shows that a good performance of the models usually depends on their ability to simulate the anomalous vertical motions and cloudiness in the SC regions，which can lead to air temperature variations. Therefore， the simulated vertical motion and cloudiness anomalies in the eastern SC in response to the QXP AHS anomalies are the key circulation factors affecting the model’s performance in simulating the HWF-AHS relationship.