This invention relates to a determination method for the diffusion sphere of the explosive gas of a liquid socket when falling including: 1, setting up a set of information system suitable for socket flying regions including: digitalizing landforms of flied regions and setting up a geographical information system, imaging the landform information of the geographical information system into an emission coordinate system to collect information of cities, roads, plants, schools and populations, initializing the weather information of the regions, positions and the flying time into an information system, determining the toxin grade information of a liquid socket propellant, 2, determining the diffusion sphere of the explosive gas at falling of the socket including the determination of the source strength of the propellant, the air wind field of a complicated landform and the diffusion concentration. |