Abstract: According to self-built testing system of water mist explosion suppression, the lowest explosive limits of gas in different granularity and flow rate of the water mist are studied respectively, based on the test results, the suppression process of granularity and flow rate of water mist on gas explosion is analyzed in theory, the suppression effect of destruction collisions between water mist and free radicals on the gas explosion reaction is less than other factors. The results indicate the influence law of granularity and flow rate of water mist on the lowest explosive limit of gas is that the smaller the granularity of water mist is; the more the flow rate of water mist is, the higher the lowest explosive limit of gas is; grained parameters of water mist play a leading role in the lowest explosive limit of gas, flow parameters of water mist play a secondary role.