Based on the thermal dose criterion, the mathematical model of flash fireball is established. Using MATLAB programming, the thermal radiation dose of dynamic flash fireball is calculated programmatically. The influences of leakage aperture, pipeline operating pressure and ambient temperature on the thermal radiation hazard range of the fireball are studied, and the boundary range of eight hazard areas under the studied conditions is obtained according to the critical thermal radiation dose. The results show that the critical thermal radiation hazard radius of flash fireball is approximately linearly positively correlated with the leakage aperture and pipeline medium transportation pressure, and the leakage aperture exhibits the greatest influence on the critical thermal radiation hazard radius.