Abstract: In the process of coal production, the coal spontaneous combustion, secondary explosion can easily lead to high temperature environment. In order to study the change laws of gas explosion limits under extremely high temperature conditions, gas explosion limits at 25 ℃,100 ℃,200 ℃,300 ℃,400 ℃initial temperature conditions were tested by the gas explosion characteristic test system of 1 L extremely high temperature. The results showed that gas explosion limits and the initial temperature are roughly linear relationship in the range from 25 ℃ to 400 ℃. When the initial temperature changed from 25 ℃ to 400 ℃, the gas explosion upper limit increased by 7.7 percentage points, and the lower explosion limit dropped by 1.53 percentage points. With the initial temperature increasing, the gas explosion range increased, the risk of gas explosion increased. The research conclusion provides a theoretical basis for preventing gas explosion accidents under extremely high temperature conditions.