By employing the TNT equivalent model to simulate the internal vapor cloud explosion of storage tanks, the internal explosion flow field and the internal explosion loading on the tank wall for dome-roof steel tanks are numerically simulated in this paper. Firstly, considering the tank wall as a rigid wall, the distribution and magnitude of internal explosion loading are analyzed under different cases. The effect of the fluid-structure interaction between the explosion flow and the tank wall on the explosion loading is next examined. It has been shown that, the maximal explosion loading appears at the center zone of the dome-roof, and usually is just the second reflected overpressure peak value, while for other zones the maximal explosion loadings are the first overpressure peak values. The effect of fluid-structure interaction has little influence on explosion loading, it is thus reasonable to adopt the uncoupled model for approximate calculation.