Abstract: The Dianchi basin is the most intense area of human activity in Yunnan Province, and inevitably faces enormous pressure on the water environment in the process of economic development. The study of the spatial and temporal variability of the water environment in the Dianchi basin and the mechanisms of its changes are important for further balancing the relationship between development and conservation. This paper successively analyses the spatial and temporal variability of water quality in the main rivers entering the Dianchi basin and the spatial variability of ecological health of Dianchi Lake, and analyses the driving factors using geographic probes. The results show that there is significant spatial and temporal variation in the water environment of the Dianchi basin: (1) From 2010 to 2020, the water quality of the major rivers in the Dianchi basin has improved significantly. From 2010 to 2015, we saw significant elimination of poor category V rivers while from 2015 to 2020 we saw a shift to category II and III water quality in more rivers. (2) In 2020, there is spatial heterogeneity in the quality of the water environment. The water quality of Caohai is better than that of the Waihai, but the lake itself is in a sub-healthy state. (3) Changes in the quality of the water environment in the Dianchi basin are influenced by a combination of factors, of which policy optimisation and pollution reduction and expansion are the best solutions to improve the water environment in the Dianchi basin, and the interaction of population and construction land growth has put greater pressure on the water environment in the Dianchi basin.