Abstract: Based on the Mohr-Coulomb strength theory, indoor triaxial tests was conducted by setting up multiple control groups to study the physical properties, shear strength differences and related influencing factors of brown coniferous forest soil and dark brown soil in Daxing’an Mountains. The results showed that there were differences in water content, soil bulk density and mechanical composition between the two research objects and different soil layers. Soil shear strength was affected by soil bulk density, mechanical composition and root addition. Among them, soil shear strength was significantly negatively correlated with silt content（R=-0.755 3） and positively correlated with sand content（R=0.978 4）. The cohesion was significantly positively correlated with the sand content（R=0.760 1）, the internal friction angle was significantly positively correlated with the clay content（R=0.836 0）, and was significantly negatively correlated with the silt content（R=-0.815 9）. The ‘ reinforcement’ effect of root system contributed to the improvement of soil shear strength, which increased the internal friction angle of brown coniferous forest soil and dark brown soil, decreased the cohesion of brown coniferous forest soil, and increased the cohesion of dark brown soil, resulting in varying degrees of changes in soil shear strength. However, both soils showed increasing shear strength under high radial confining pressure.