Strontium-rich groundwater exists in the underlying carbonate rocks of the Tianjiazhai Shimachuan River basin, Fugu, China. In this study, the hydrochemical characteristics and formation mechanisms of Sr-rich groundwater were assessed using mathematical statistics and traditional water chemistry, combining geological and hydrogeological conditions, as well as hydrogeochemical theory. The results showed that the Sr²⁺ content range in Sr-rich groundwater was 0.85~2.99 mg·L⁻¹, which is weakly alkaline fresh water. HCO₃⁻ Ca·Mg·Na was the main facies type of Sr-rich groundwater. Sr-rich groundwater has relatively stable contents of chemical elements. The water–rock interaction was the main factor controlling the hydrochemical characteristics of Sr-rich groundwater, particularly carbonate dissolution, influenced by some degree of cation exchange. The Sr element in groundwater mainly comes from the dissolution of the sandstone of the Yanchang Formation. The higher the degree of weathering and the longer the water–rock reaction time, the more favorable the dissolution and enrichment of Sr in groundwater. Moreover, the large weathering thickness and fracture development of the rocks in the Tianjiazhai area provide favorable conditions for the formation of Sr-rich groundwater. The results of this study provide a scientific basis for developing effective policies to protect Sr-rich groundwater resources.