Abstract: The upper reaches of the Han River basin serve as a crucial water source for the middle route of the South-to-North Water Diversion Project. Understanding the hydrochemical characteristics and major ion sources of the surface water is of great significance for ensuring the water supply safety. This study quantitatively analyzed the hydrochemical composition characteristics and the main control factors of surface water in the Shaanxi section of the Han River basin. A total of 46 sets of surface water hydrochemical data were collected. The methods used included mathematical statistics, ion ratio analysis, graphical methods, and the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) receptor model. The results showed that the dominant cations in the surface water were Ca2+, with HCO3- and SO42-as the dominant anions. The pH values ranged from 7.53 to 8.81, with an average of 8.18. The TDS values ranged from 107 to 451 mg/L, with an average value of 187 mg/L. In terms of spatial distribution, the average mass concentrations of TDS and pH in tributaries were higher than those in the mainstream. The average mass concentrations of major ions and TDS values in the three prefecture-level cities followed the order: Shangluo City > Hanzhong City > Ankang City. The main hydrochemical type of surface water in the study area was HCO3-Ca. The hydrochemical components of surface water were mainly influenced by rock weathering and human activities, with weak cation exchange. Rock weathering was dominated by the dissolution of carbonate and silicate rocks. The impact of human activities on the hydrochemical evolution was mainly reflected in changes in ion components such as SO42-, Cl-, NO3-, and Na+, which were primarily influenced by mining activities and agriculture activities. The APCS-MLR receptor model revealed that the main sources of surface water hydrochemical components were silicate rock dissolution and mining activities, evaporative salt rock dissolution and domestic sewage, carbonate rock dissolution and agricultural activities, and other sources, which contributed 33.75%, 13.67%, 30.87%, and 21.71%, respectively to the surface water of the study area.