Abstract: In this paper, by analyzing the order of magnitude, the flowprocess of the leaking LPG is simplified into three independentsub-processes, including the process of LPGsedimentation to floor; spreading to other room and diffusing to roof, thena simplified method for forecasting concentration distribution of indoorexplosion gas is put forward. The feasibility and simplicity of this methodare discussed by applying it to analyzing an actual LPG explosion hazard.