In order to study the power of one RDX-based aluminized explosive with different charge diameter, the cylinder tests with diameters of 25.4 mm and 50.0 mm were conducted. The experimental results show that the expansion velocity of Φ50.0 mm cylinder is 4.73% higher than that of Φ25.4 mm when the relative volume of detonation product is 10. By using the dynamic finite element program LS-DYNA, two cylinder tests were simulated and the Lee-Tarver ignition and growth trinomial model was adopted. The parameters Jones-Wilkins-Lee equation of state and the reaction rate of the aluminized explosive were obtained through simulation and test results.