Plant water use plays an important role in regulating the hydrological cycle and productivity of the ecosystem. Water stress in cold temperate forests gradually is intensifying under climate change. Thus, studying characteristics in water utilization of typical tree species in cold temperate forest ecosystems is helpful to understand ecosystem stability and sustainability. In this study, in two typical forests, larch (Larix gmelinii) and birch (Betula platyphylla) forests, using the stable isotope methods, the stable isotope value of hydrogen and oxygen (δD and δ¹⁸O) of precipitation, xylem water of both larch and birch, and soil water in both forests were measured to explore distribution characteristics of δD and δ¹⁸O values in the northern Greater Hinggan Mountains. Meanwhile, combined the multi-source linear mixed model and sapwood sap flux, we analyzed the contribution of different water sources on the two species to explore the variations in water utilization characteristics of larch and birch during the growing season. The results showed that (1) the atmospheric rainfall and soil water isotopes in the study area were affected by evaporation that induced a certain degree of fractionation. However, the isotopic fractionation degree of soil water was different between the two species, which was higher in larch forest than that in birch forest. (2) Soil water content and soil water stable isotope value in the upper soil (0-10 cm) were strongly influenced by rainfall and evaporation in the two forests. The soil water stable isotope value in each layer showed significant differences (P <0.05). (3) In May and September, the soil water utilization of larch and birch was mainly from the upper layer. The soil water utilization rates were 64.7% and 61.3% in larch and 61.5% and 66.0% in birch, respectively. The average daily utilization was 2.00 kg/d and 1.10 kg/d in larch and 6.74 kg/d and 2.75 kg/d in birch, respectively. From June to August, soil water utilization was mainly from the lower layer (20-40 cm). The utilization rates of were 69.1%, 69.0%, and 93.3% in larch forest and 73.5%, 86.4%, and 87.0% in birch, respectively. The average daily utilization was 4.01 kg/d, 3.96 kg/d, 5.16 kg/d in larch and 16.35 kg/d, 20.06 kg/d, 16.52 kg/d in birch, respectively. Our study suggested that there was a similar water source but a different water utilization rate between the two species. This difference was mainly from the water utilization from June to August when the water utilization rate from the lower layer of birch was significantly higher than larch. Thus, in the context of intensive water stress, the larch will have stronger viability than the birch.