The safety of styrene tank farm whose harm was serious was evaluated by Dow Chemistry Method. According to the actual situation of tank farm, the typical storage tanks to be evaluation units were selected, then the risk coefficient of technologies was analyzed, and the fire-explosion index, exposure radius and regions were calculated. The fireexplosion index and class could be effectively reduced by some safety measures compensating. The results showed that this method could comprehensively and effectively evaluate the potential fire and explosion hazards in the styrene tank farm.