To study the propagation rule of blast shock wave outside tank and its impact on the safety of storage tank, the software LS-DYNA was used to build numerical model of dynamite-storage tank, and the air blast numerical calculation was performed. The study analyzed the attenuation relation of shock wave overpressure and the dynamic response of the tank. The reliability of the model was verified by contrast with the empirical formula. And the further amendment for numerical simulation results was made. The results are as follows: When shock wave moves to burst surface center, principal stress in 10ms quickly reaches maximum value, and then decreases rapidly and continuously oscillated; The facing blasting center first produces larger tensile stress, the destruction of concrete tank belongs to brittle failure; When the proportion distance is greater than 1, overpressure formula can better fit the attenuation law of overpressure; While the proportion distance is less than 1, the error of the overpressure formula is large. The amended overpressure calculation formula can be used as a reference tank blast-resistant design.