Abstract: To reveal the distribution characteristics and sources of fluoride in the water environment of Xianghai Reservoir, this study summarized the inter-annual and monthly variation characteristics of fluoride and the current status of soil fluoride content by reviewing historical monitoring data of water fluoride from 2012 to 2021 and monitoring soil fluorine content. The results showed that the average annual concentration of fluoride in the water environment of Xianghai Reservoir decreased from 3.92 mg/L in 2012 to 2.04 mg/L in 2021, with an average concentration of 3.03 mg/L, which was significantly higher than the threshold of 1.5 mg/L for Class V surface water quality specified in “GB 3838—2002”. The average total fluoride contents in soil were 2067.12 mg/kg and 1013.91 mg/kg, respectively, far exceeding the national background values. Through the analysis of topography, climate, water system distribution, environmental factors, and regional river characteristics in the Xianghai Reservoir area, the sources of fluoride in the water environment were identified. This study provides objective and impartial baseline data for the evaluation of Xianghai Reservoir and offers scientific and technical support for pollution prevention and control in high-fluorine lakes and reservoirs in the semi-arid western region of Jilin Province.