The world is getting hotter and hotter, causing more and more heatwaves. It is very important to study how these factors affect the environment, for example the nutrients in lakes, the concentration of chlorophyll-a(Chl.a) in water, and the growth of phytoplankton. This will help us to understand how lakes respond to and recover from heatwaves, and it will provide scientific support for the management and regulation of lakes under climate change. This study used the GOTM-WET model to see what effect the 2022 summer heatwave had on the amount of Chl.a in northern Lake Taihu. It looked at how different levels of heatwave intensity affected Chl.a and what might be causing this. The results showed that the 2022 summer heatwave greatly reduced the concentration of Chl.a in water, and the effect of this was stronger with the higher heatwave intensity. Further analysis showed that the maximum water temperature during the 2022 heatwave exceeded 37 ℃, which could have been too hot for most algae to grow. The heatwave also made the water more mixed up, with less nitrogen and phosphorus in the surface layer and more in the bottom layer. This meant there was less nutrition available for surface algae growth, which also meant there was less Chl.a. This study looked at how water temperature and nutrients can affect the growth of algae in lakes when it is very hot. It helps us to understand more about how heatwaves affect the natural processes in lakes.