Taking the 3000-m3 vertical vault storage tank as the research object, the finite element calculation method is used to calculate the pressure and temperature of the fluid during the explosion of the tank. By calculating the structural response of storage tank using multi-field coupling method, the distribution of stress and the deformation of tank are obtained. The tank frangible roof performance influenced by explosion load in different working conditions is analyzed. The results show that the failure pressures of the tank roof are the same in empty-tank, half-tank and full-tank conditions, and the damage pressure of the tank shell and bottom gradually increases with the storage liquid level. Temperature also affects the failure pressure at different locations. At the same location, the higher the temperature, the lower the failure pressure. When the tank is empty, the failure times of the roof and the bottom are almost the same, the failure time of tank shell is obviously earlier than that of other locations. The intensity ratio k is less than 1.5, which means the tank does not have frangible roof performance. For the liquid level of half tank and full tank, no matter where the explosion point is, the failure pressure at the roof-to-shell location is smaller than other locations, and the failure time at the roof-to-shell location is obviously earlier than other locations. The intensity ratio k is bigger than 2.5, which means the tank have frangible roof performance.