Abstract: The relationship between surface water and groundwater is an important content of the research on the water cycle and water resource management. The methods of field water sampling and laboratory analysis were combined with the stable isotopes (δD, δ¹⁸O) and hydrochemistry to study the relationship between surface water and groundwater in the second Songhua River basin. The spatial difference of stable isotopes in the surface water and groundwater was obvious. The water samples in the upstream were isotopically depleted, but isotopically enriched in the downstream. The evolution of water type ranged from the Na-HCO₃ type in the Changbai Mountain area to the Ca-Mg-HCO₃ type. However, the evolution of water type was Ca(Mg)-Cl(SO₄) impacted by human activities. The two-component method was used to calculate the quantitative relationship between surface water and groundwater. The deep groundwater was recharged from the river and shallow groundwater, and the contribution of shallow groundwater was about 50%. The contribution of the shallow groundwater discharged to the river was about 20% in the plain area. The results could provide the theoretical basis for the comprehensive utilization of surface water and groundwater, and the sustainable utilization of water resources.