Abstract: With the shortage of the gasoline resource day by day，the adjustment of county’s energy strategy，environment protect requirement and the continuous progress of the automobile technology，more and more automobiles are designed on the CNG as their fuel and corresponding CNG stations are increasing at the same time.But the consequential accidents such as the leakage of the gas and the fire disaster make the security of the CNG station become a serious problem which people pay more and more attention on it.If the gas is not fired immediately，it may construct the gas cloud cluster and will explode when it comes out a fire，and people in a certain distance may be wounded by the shockwave also the architectures in the dangerous range will be destroyed.This paper contributes to formulate the evacuate conditions for pedestrian after the explosion accident happening and also provides the basis for evaluating the new constructed CNG stations.