Abstract: In order to study the influence of roadway cross-section mutation on the shock wave propagation and the destruction of shock wave overpressure impulse, based on the experiment and numerical simulation, by using self-built experimental system for the propagation of coal and gas outburst shock wave and combining with the establishment of three-dimensional numerical model of shock wave propagation in varied-section roadway, the propagation law of outburst shock wave under different initial gas pressures was studied. The results showed that the pressure change in the roadway after outburst is divided into two stages of the initial stage of shock disturbance and the pressure attenuation stage, the results indicated that the peak value of the overpressure in the initial stage of shock disturbance is greater than the pressure attenuation stage. However, the overpressure impulse of the former is less than that of the latter, taking the initial pressure of 0.6 MPa as an example, the calculation results showed that the overpressure impulse of the pressure attenuation section is 52.4% higher than the initial stage of shock disturbance. Moreover, with the propagation of shock wave in the roadway, the total shock wave impulse appears to decay first and then increase. After outburst, the shock wave overpressure attenuates with distance first; in the process of the shock wave being introduced into the small diameter roadway from the large diameter roadway, a local high pressure area was formed due to wall reflection, which makes the overpressure strength rise at 0.65 m in front of the cross-section, showing a change rule of attenuation first and then increase.