Abstract: This paper investigated the hydrochemical and stable isotopic characteristics of surface water, underground water in the interflow zone, and groundwater in the Maozhou River Basin, as well as the interactive relationship between surface water and groundwater, and the accuracy of the interactive relationship was verified using a network of monitoring wells. The results indicated that the hydrochemical type of surface water of the Maozhou River Basin was gradually transited from Ca² —Na —Cl^- in the upstream to Na -Cl^- in the downstream; the hydrochemical types of groundwater from near to far and shallow to deep, which were mainly characterized by Ca² —Na —Cl^- and Ca² —Na —HCO₃^-—Cl^-, and gradually transited to Na -Cl^- type in the downstream; the differences between the anions and cations in groundwater and surface water were increasing, as well as the hydraulic connection between surface water and groundwater was gradually weakening influenced by the seawater tidal action. The slopes of surface water, underground water in the interflow zone, and groundwater were all smaller than the coastal atmospheric precipitation line in Guangdong Province, and the hydrogen and oxygen stable isotope data points were mainly concentrated in the top left of the coastal atmospheric precipitation line in Guangdong, indicating that evaporation was more intense. Based on the analysis of the relationship between Cl^- and  with spatial distance, surface water was primarily replenished by groundwater discharge in the upstream of the Maozhou River Basin; there existed a relatively stable replenishment and discharge relationship between surface water and groundwater in the middle and upper reaches, with a close hydraulic connection, and the surface water mainly recharged by the groundwater, which also confirmed by the water level analysis of the network of monitoring wells in the middle reaches; the interactive relationship between surface water and groundwater was gradually weakening, but groundwater discharge still replenished surface water. The conclusions of this study could provide reference for the long-term governance of water environment and the development and utilization of water resources in Maozhou River Basin.