In this study an experiment system was built to explore the suppression of methane/air explosion in pipe via water mist. And droplet size of water mist and pipe size were investigated to shed light on their influence on explosion. It was found that for water mist droplet diameter of 45 gm and 100 gm it was impossible to suppress the explosion. Instead it promoted the explosion and the larger the diameter, the more easily the gas exploded. But it was effective to suppress the explosion with the presence of fine water mist with droplet more than 160 mu m in diameter and the larger the ratio of the pipe length to its diameter, the better its effectiveness in decreasing flame propagation velocity and suppressing gas explosion. This study can provides theoretical foundation for the designing of water mist explosion suppression system in different industry occasions. (C) 2017 Elsevier Ltd. All rights reserved.