The invention discloses a method for determining the leakage 
pollution range of a hazardous 
chemical substance, and the method comprises the following steps: s1, determining a 
simulation scene, and obtaining the meteorological and hydrological information, 
geographic feature information and leakage source information of a leakage accident generation region; s2, establishing a three-dimensional geometric model of an area near the leakage source, and performing 
mesh generation; s3, importing the grid into a fluid flow module in 
finite element analysis software; s4, setting material characteristics and boundary conditions in 
finite element analysis software according to the information acquired in the step s1, meanwhile, judging whether the leaked substances have 
phase change or not, and setting an inter-phase 
mass transfer model according to the 
phase change type; s5, selecting an appropriate convergence condition and a sub-
relaxation factor, calculating a step length, and carrying out numerical calculation; and s6, after calculation is finished, analyzing a result to obtain concentration field distribution, 
diffusion velocity field distribution and 
diffusion path data of the leakedsubstances. According to the method, the 
diffusion ranges of the liquid-phase hazardous 
chemical substance and the 
vapor cloud thereof can be determined at the same time, and a hazardous 
chemical substance concentration distribution cloud chart is provided.