Abstract: To study the harm of gas explosion overpressure and gases after explosion, the 20 L gas explosion characteristic test system and gas chromatograph are used to study the pressure and the change laws of the gas after the gas explosion under different initial gas volume fraction conditions. The study found that the initial volume fraction of gas explosion at the optimum explosion volume fraction is the most harmful to the human body; the H₂ and CO generated after the explosion will promote the explosion of gas and have a function relationship with the initial gas volume fraction. The volume fraction of H2 after high-volume fraction gas explosion will be within the limits of H₂ explosion; the CO produced by the explosion will cause human poisoning to die, and CO₂ and low volume fraction of O₂ will cause people to suffocate.