Abstract: Based on the comparative analysis of the main calculation models for gas leakage and diffusion simulation,the slab model Was selected to make a simulated calculation of the continuous leakage of liquefled petroleum gas(LPG).For the two situations of medium leakage and large leakage,a comparison was made between the result calculated by slab model and that gotten by SAFETI risk assessment software,developed by Det Norske Veritas(DNV).The analysis shows that,in the calm wind conditions.the simulation result of the leakage and diffusion of LPG with slab model is more accurate;but with the deereasing of clouds density,the calculation deviation with slab model gradually increases,and the deviation will increase with the increasing of wind speed.So,the simulation result gained by slab model must be revised.