Aiming at providing the information to quantify the potential severity of deflagration, vessels which can withstand the risk of explosion during gas fuel processing, storage and transportation. Under different initial temperatures (298K-373K) and the concentration of other four combustible gases (CO, H2, C2H4, C2H6, 0.4%-2.0%), the explosion pressure characteristic parameters of 7% and 11% methane were obtained in a 20L spherical gas explosion system. In addition, the change trend of the H·, O· and ·OH radical volume fractions of the mixed gas of different components during the explosion process was analyzed and simulated, and the sensitivity analysis was performed by using the CHEMKIN-PRO software. The results show that under the constant concentration of the other four combustible gases, the maximum explosion pressure decreases linearly with initial temperature increasing, and the maximum pressure rise rate is almost constant or decreases. At the same initial temperature, for a 7% methane-air mixture, as the concentration of the other four mixed gases with CO as the main component increases to 2%, the maximum explosion pressure and the maximum pressure rise rate show an increasing trend. But that of the 11% methane-air mixture appear a decreasing trend. The maximum mole fraction of free radical H·, O· and ·OH with the increases of combustible gas concentration when it is in the 7% methane-air mixture during the explosion. In the 11% methane-air mixture, the maximum mole fraction of O· and ·OH radicals showed a downward trend. The key elementary reaction step R53 promotes the generation of methane and the consumption of free radicals (O· and H·).