Abstract: This paper introduced the classification standards of chemical accident hazards used in ALOHA(areal locations of hazardous atmospheres)software and the use guideline of this software. Taking example of leakage of toluene and liquid chlorine, the calculation results for the accident consequences using this software were present. The results showed that the possibility of vapor cloud explosion, the scope of damage and toxicity of boiled liquid evaporate vapor explosion (BLEVE) when toluene leakage occurred under certain conditions. The danger of liquid chlorine to human body under certain conditions and at different distances from the leakage source was also clearly shown. We can organize people to evacuate the hazard area according to the scope of toxic leakage hazard simulated by ALOHA software, while we make the chemical emergency rescue plan and site decision-making for the emergency response team based the calculation results of ALOHA software.