Abstract: In order to accelerate the utilization of low-pollution water resources in Lake Erhai Basin and promote the protection of water resources, water environment and water ecology in the basin, the total amount of low-pollution water in Lake Erhai Basin in 2021 was calculated from two aspects: the tailwater of urban sewage treatment plants and the runoff and drainage of farmlands, based on the relevant data of urban sewage treatment plants, meteorological data and agricultural irrigation in Lake Erhai Basin in 2021. Combined with the actual investigation, the reuse status and unused amount were analyzed. The results showed that the total amount of low-pollution water produced in Lake Erhai Basin was 239.171 6 million m³, and the total amount of low-pollution water reused was 8.565 1 million m³ in 2021. In the eastern region, the proportion of tailwater reuse was the highest, which was mainly used as landscape water; in the southern region, the tailwater reuse objects were all for urban utility purposes; in the western region and the northern region, the tailwater reuse objects were agricultural irrigation. The unutilized amount of low-pollution water in Lake Erhai Basin was 230.606 5 million m³, of which the unutilized amount in northern and western areas was the largest, accounting for 45.03% and 42.86%, respectively. In the northern region, low-pollution water can be recycled for farmland irrigation through the established "northern three rivers" riverside belts, reservoirs and wetlands; in the western region, low-pollution water can be recycled for farmland irrigation through the established reservoirs, wetlands and storage belts; in the eastern region, stormwater runoff and tailwater can be reduced into the lake through the established stormwater storage facilities to reduce low-pollution water. In the southern area, low-pollution water can be used for farmland irrigation and industrial wastewater recycling through the small upstream reservoirs that have been built. In order to effectively promote the reuse of low-pollution water in Lake Erhai Basin, it was suggested to make continuous efforts from three aspects: strengthening the policy guarantee of low-pollution water reuse, conducting monitoring and risk assessment for low-pollution water quality and quantity, and strengthening regional low-pollution water resource allocation engineering measures. It was also proposed to accelerate the construction of a low-pollution water recycling and reuse system, make full use of low-pollution water reuse supporting facilities, optimize management and operation, and increase the amount of low-pollution water to reduce the pollution load into the lake, thus achieving the goal of protecting Lake Erhai.