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Marine heatwaves (MHWs) are prevalent in the South China Sea (SCS) and are primarily caused by the anomalous western Pacific subtropical high (WPSH) which suppresses the SCS summer monsoon. Our study investigates future summer MHWs in the SCS in response to the enhanced WPSH. The results show that the WPSH will be strengthened in most models under the highest emission scenario. Total days of summer SCS MHWs will significantly increase with the enhancement of the WPSH and peak at the end of the 21st century. The high‐value area of total days of summer MHWs (>50 days) appears in the south‐central SCS. The intensity of MHWs exhibits little response to the strengthening WPSH. In addition, the weakening of the SCS cold filament due to the anomalous WPSH also favors summer MHWs. Furthermore, increased future severe summer SCS MHWs will create a higher bleaching risk for coral reefs. Plain Language Summary: Marine heatwaves (MHWs) can have devastating impacts on marine ecosystems when seawater temperatures are warmer than the 90th percentile for at least five consecutive days based on a fixed 30‐year (or longer) baseline. The western Pacific subtropical high (WPSH) is an anticyclonic system in the northwestern Pacific that affects MHWs in the South China Sea (SCS). Based on the latest climate models, we calculate the total days and intensity of summer MHWs in the SCS under increased variability in the WPSH in future projections. Total days of summer MHWs will rapidly increase and peak at the end of the 21st century. Furthermore, the total days of summer MHWs are associated with SCS upwelling and cold filament, which is also influenced by strong WPSH. More concerning are the increases in severe summer MHWs, which will make coral reefs more susceptible to bleaching in the SCS in the future. Key Points: Increasing variability in the western Pacific subtropical high (WPSH) leads to more frequent, stronger WPSH events in future projectionsThe total days and intensity of summer marine heatwaves (MHWs) in the South China Sea (SCS) show different responses to the enhanced WPSHTotal days of summer MHWs in the SCS increase with the strengthened WPSH, resulting in a high coral bleaching risk [ABSTRACT FROM AUTHOR]