Abstract: The Maozhou River is a typical tidal river. Understanding the recharge sources, hydrochemical and stable hydrogen-oxygen isotope composition characteristics, and evolution processes of surface water and groundwater in the river basin, and clarifying the interactive relationship between surface water and groundwater, can provide a scientific basis for the long-term governance and operation of tidal river water environment. During the dry season, we collected 52 sets of samples of surface water, hyporheic zone water and groundwater in the Maozhou River Basin. Based on multivariate statistical analysis, the Piper trilinear diagrams, and stable hydrogen-oxygen isotope ( \delta \rm D , \delta ^18\rm O ) analysis, we analyzed the hydrogeochemical compositions and \delta \rm D\text -\delta ^18\rm O trendline characteristics of river water, hyporheic zone water, and groundwater, and systematically revealed the recharge sources and interactive evolution mechanisms of river water and groundwater. The results showed that the main anions and cations of surface water, hyporheic zone water and groundwater were Cl⁻、HC\mathrmO_3^- and Na⁺、Ca²⁺; the hydrochemical types transit from Ca²⁺-Na⁺-Cl⁻ and Ca²⁺-Na⁺-HC\mathrmO_3^- -Cl⁻ in the upper reaches to Na⁺-Cl⁻ in the lower reaches; the groundwater level first decreased, then rose, and then decreased again from the upper to middle and lower reaches, and the groundwater level was obviously higher than the river water level in the Yanchuan section of the middle basin. The total dissolved solids (TDS) and Cl⁻ concentrations of river water (2 080-4 210 mg/L and 51-3 139 mg/L, respectively) were generally higher than those of groundwater (64-1 460 mg/L for TDS and 7.7-936 mg/L for Cl⁻). The TDS and Cl⁻ concentrations of groundwater samples along the river first decreased, then rose, then decreased again, and finally rose, which was consistent with the variation trend of mainstream river water samples. The \delta \rm D and \delta ^18\rm O values of river water, groundwater and hyporheic zone water all fell near the Guangdong coastal precipitation line, and the global meteoric water line; the slopes of \delta \rm D\text -\delta ^18\rm O relationship trendlines increased sequentially, with the values being 3.644 0, 4.521 1 and 4.859 9, respectively. The \delta ^18\rm O values of groundwater and river water first decreased and then increase along the flow path, with groundwater \delta ^18\rm O values being higher in the upper and middle reaches, and river water \delta ^18\rm O values being higher in the lower reaches. This study indicates that atmospheric precipitation is the main recharge source of surface water and groundwater in the Maozhou River Basin. During the runoff process, water bodies are mainly affected by silicate mineral weathering, dissolution and evaporation. The groundwater discharge primarily recharges river water in the upper reaches; the groundwater recharge effect weakens in the middle reaches: and the river water mainly recharges groundwater in the lower reaches. Overall, the Maozhou River Basin is dominated by groundwater discharge that recharges river water.