To reveal the characteristics of groundwater circulation in typical watersheds of the northwestern Beijing-Tianjin-Hebei region, this paper used environmental isotopes and hydrochemical techniques to analyze the characteristics of hydrogen and oxygen isotopes, hydrochemical characteristics and spatio-temporal changes, as well as the relationship between surface water and groundwater transformation in different watersheds of the Zhangjiakou region. Results showed that the surface water in the region was mainly HCO3-Mg·Na and HCO3·Cl-Na type, while in different seasons the water types of the groundwater were not the same. Specifically, the groundwater types were more diverse with HCO3-Mg·Na, HCO3·Cl-Na, HCO3·Cl-Na·Mg types. An ion source analysis indicates that the surface water and groundwater were mainly affected by rock weathering. Parts of the groundwater in Zhangjiakou were affected by evaporation concentration. The hydrogen and oxygen isotopic compositions of surface water and groundwater were similar, indicating that the water was mainly from the atmospheric precipitation. Based on stable isotopic characteristics, 37.74% of the groundwater in the study region was derived from precipitation, while the remaining 62.26% was from river water, suggesting that the basin groundwater is mainly recharged from the river water.