Abstract: The exploration of the eco-environmental effects caused by land use transition is of great significance to promote the sustainable development of regional economy and improve the eco-environment. Taking the Taihu Lake city cluster as an example, this paper used the GIS spatial analysis method and integrated the measurement results of the eco-environmental quality index and ecosystem services function to reveal the eco-environmental effects brought about by land use transition and identify salient regions. The results showed that: (1) During 2000-2018, the transition from agricultural production land to living land was the main feature of the land use transition, with a total of 3 054.3 km2 transferred out, and the overall change in ecological land was slow, but the area of water ecological land fluctuated considerably. The order degree of land system in the suburbs of Southern Jiangsu had increased rapidly, and the disorder degree of land use in the northeast and south of the study area had increased; (2) The overall eco-environmental quality continued to decline from 0.407 to 0.392. The regional habitat quality decreased from 0.328 to 0.303. The high-value areas of carbon sequestration were concentrated in the southwestern part of Huzhou, while the low-value areas were concentrated in the northeastern part of Suzhou. The total water supply rose from 157.33 billion m3 to 165.41 billion m3. The high-value areas of recreational services were concentrated in the southwestern part of Huzhou and around Taihu Lake, while the low-value areas were concentrated in the centre of Taihu Lake and the southeastern part of Jiaxing; (3) The average eco-environmental comprehensive index had decreased by 0.026. The decline was the most serious in the middle of Suzhou, forming extensive cold spot regions. The eco-environmental status in the east of Zhangjiagang and the west of Liyang had improved, forming many local hot spot regions; (4) Four types of regions where land use transition affected the eco-environment were identified: LC-EC region was the most extensive, mainly distributing in the northeast of the region; LH-EC region was mainly distributed in the suburbs and some rural areas; LC-EH region had minimum area and were mainly distributed in Wuxi and Taihu Lake scenic area; LH-EH region was mainly distributed in Zhangjiagang and Huzhou. The results can provide a scientific reference for coordinating the development of regional land resources and improving the eco-environment.