Abstract: In deep mining, coal-rock is in a state of three unequal forces, and the intermediate principal stress has the influence on the deformation and strength characteristics of coal-rock. This study studied the deformation and seepage characteristics of gas-bearing composite coal-rock under different intermediate principal stresses by using true triaxial gas-solid coupling seepage test device for coal and rock. The results show : ① With the increase of intermediate principal stress, the strain in the direction of maximum principal stress first increases and then decreases when the peak strength is reached, and there is widening gap between the strain in the direction of intermediate principal stress and the strain in the direction of minimum principal stress.② Under low intermediate principal stress, the strain in the intermediate principal stress direction shows expansion and deformation, and when there is relatively high intermediate principal stress, the ε₂-Δσ curve reaches the peak and then bounces back, and the strain in the intermediate principal stress direction finally shows compression and deformation.③ With the increase of intermediate principal stress, the trough value of relative permeability coefficient decreases, and the peak inflection point of relative permeability coefficient curve is consistent with the inflection point of ε₁-Δσ curve.④ When the stress peak is reached, the total input energy of the specimen first increases and then decreases, which is similar to the changes of the specimen strength: The elastic strain energy first increases and then decreases, the dissipative energy continues to increase, U_e/U first increases and then decreases, and U_d/U first decreases and then increases.