Using the theory of explosion mechanics and gas detonation dynamics and the conservation law of mass, momentum and energy, the physical and mathematical models of damage effect are set up in excavation roadway during gas explosion. In view of gas concentration, accumulation position, volumes and states of spaces, the shock wave damage on structures in the roadway during gas explosion. The damage effects are characterized of heat and mechanic damage. Meanwhile, the high temperature and pressure are formed in different degree. With the action of overpressure and impulse, the damage degree is different with different geometric structures in ventilation system. By means of basic condition, influential factors, procedure features and simulation, some unnecessary structures or barriers should be cleared in order to keep smooth the ventilation system.