Abstract: This article studies the relationship between explosion pressure and flameproof enclosure with orifice, and the experimental results show that orifice causes detonation so that the explosion pressure of flameproof enclosure instantly increases and the rise time of explosion pressure is also greatly reduced. The pressure of same concentration gas has a constant speed of wave propagation and pressure is also increased at a constant speed; the maximum explosion pressure is determined by combustible gas concentration and the initial pressure.