Taking the floating roof tank of a petrochemical company,whose single tank capacity was 20000m3, for example,the thesis analyses and researches the fire and explosion accident of tank, selects typical typical fire accident model as the basis,came to the conclusion damage radius of radiation flux to personnel: From 30s to 60s, the death radius was 100m to 129.6m,and people would be hurt in different degree within a radius of 240m ,so the range of Cordon around was beyond 240m;The extent of damage to equipment:all equipments would be damage within 70m away from the burning oil tanks; The equipments beyond 85.1m had almost no effect;The damage radius to firefighters:The critical safety distance in fire fighting and rescue work was 214m.The thesis came to the conclusion of safe evacuation distance and alert limits,and put forward fire safety measures rightly through the using of hazard control mode.