Abstract: To study the shape characteristics of the coal and rock under the horizontal stress, thoroughly understand the mechanism of coal and gas outburst, the analysis and comparison of cave shape characteristics and numerical simulation results in the outburst site of Pingdingshan No.8 coal mine are made to prove the accuracy and feasibility of the numerical simulation method, furthermore, the development characteristics of the shape of the caves can be obtained under the conditions of different conditions of horizontal stress σ_H. The experimental results show that trend length and inclination length of the outburst caves increase exponentially with the increase of horizontal stress σ_H, and the trend length increases faster, when the horizontal stress σ_H reaches 28 MPa, the growth rate of the curve is obviously improved; the hole length increases linearly with the increase of the horizontal stress σ_H, and the growth rate is slow.