Hydrocarbon fires and explosions in petrochemical plants have occurred repeatedly every year. But domestic law of fire protection system is insufficient for the worst case scenario. In this study, we analyzed domestic and foreign standards of fire protection system in petrochemical plants and surveyed firefighting equipment of 32 petrochemical plants in ulsan petrochemical complex. Finally, it is necessary to design fire water supply based on the worst case scenario in petrochemical plants and firefighting equipment such as fixed water spray system, elevated monitor nozzle, water curtain, large amount foam monitor system should be installed for the worst case scenario in petrochemical plants.