Aiming at the problem of increasing permeability of coal seam by deep-hole cumulative blasting under in-situ stress, based on the analysis of stress field of surrounding rock and stress of blasting crack surface, the process of cumulative blasting and crack development characteristics under different confining pressures were numerically simulated. Through the field tests of cumulative blasting under different buried depths, the influence of in-situ stress on the cracking and permeability enhancement effect of coal seam deep hole cumulative blasting was discussed. The results show that the role of in-situ stress in different stages of radial crack expansion of coal seam deep-hole cumulative blasting is quite different. Before blasting, the stress state and deformation characteristics of borehole surrounding rock are determined by borehole shape and in-situ stress. In the initial stage of cumulative blasting, the impact of cumulative blasting on surrounding rock is obviously stronger than in-situ stress. Therefore, the expansion direction of blasting cracks in the initial stage is mainly determined by the cumulative structure, and directional cracks are formed along the opening direction of cumulative charge groove. With the crack extending around, the blasting effect is gradually weakened, and the in-situ stress is dominant. The surrounding rock of the borehole produces tangential compressive stress under the in-situ stress, which limits the radial crack expansion of blasting. Meanwhile, the coal cracks which are not collinear with the principal stress gradually deflect towards the direction of the maximum principal stress under the action of strong shear stress. When the equivalent dynamic stress produced by blasting can not continue to further compress the coal, the elastic strain energy accumulated in the surrounding rock of the borehole begins to release towards the blasting center, causing the coal to crack and produce new cracks. In addition, the crack expansion range in different directions is controlled by the lateral pressure coefficient. When the vertical principal stress is constant, the crack range in the direction of minimum principal stress further decreases with the increase of lateral pressure coefficient.