[Objective] Lingjiang River is an important river basin in Southern Zhejiang Province, which is typical and representative. The hydrochemical characteristics, evolutionary mechanism and irrigation suitability of surface water at Lingjiang River basin were analyzed in order to provide scientific basis for agricultural irrigation, ecological protection and high-quality development in this region.[Methods] Mathematical statistics, Piper three-line graphs, principal component analysis, and ion ratio were used to analyze the hydrochemical statistics and identify the causes of the surface water in the basin. The suitability of surface water for irrigation was evaluated by constructing Wilcox diagrams and USSL diagrams.[Results] ① The hydrochemical types of surface water at Lingjiang River basin were spatially zoned, and the hydrochemical types from HCO₃-Ca type to Cl-Na type transitioned from the middle and upper reaches (zone Ⅰ) to the lower reaches of the Wenhuang Plain (zone Ⅱ) to the estuary of Taizhou Bay (zone Ⅲ). ② The hydrochemical characteristics of the surface water in zone Ⅰ were mainly affected by the dissolution of silicate rock during rock weathering, and were affected to a lesser extent by the dissolution of carbonate karst. The hydrochemical characteristics of surface water in zone Ⅱ were mainly affected by the dissolution of silicate rock. The hydrochemical characteristics of surface water in zone Ⅲ were mainly affected by the dissolution of evaporative salt rocks. ③ The K⁺ and Na⁺ of the surface water in zones Ⅰ and Ⅱ were mainly from the dissolution of silicate minerals. Ca²⁺, Mg²⁺, HCO^-₃, and SO^2-₄ mainly resulted from the dissolution of silicate rock, and a small amount resulted from the dissolution of carbonate rock, NO^-₃ was mainly derived from human activities. ④ The surface water in zones Ⅰ and Ⅱ was suitable for agricultural irrigation, while the surface water in zone Ⅲ was poorly suited for irrigation, and could easily cause saline-alkali damage.[Conclusion] The hydrochemical components of surface water at Lingjiang River basin were affected by natural dissolution and human activities. The surface water in the river network area of the middle and upper reaches and lower reaches of the Wenhuang Plain is suitable for agricultural irrigation, while the surface water in the estuary of Taizhou Bay is prone to saline-alkali damage. Attention should be paid to the planning of agricultural irrigation and ecological protection and high-quality development.