In order to study the energy output character of shelled explosive in confined water area, a combination of physical experiments and simulation modeling was used to carry out numerical simulation of the underwater explosion of PBX-2explosive. First, aΦ50 mm cylinder test was used to obtain the JWL(Jones-Wilkins-Lee) equation of state parameters of the explosive PBX-2. Then a numerical model was constructed in commercial software ANSYS AUTODYN, which considers the hydrostatic pressure gradient and boundary conditions including free surface, side wall and water bottom were all considered. Underwater explosion of PBX-2 explosive in water pool of Φ12 m × 9.5 m were calculated by using the model above, and also the underwater explosion test was done. The results show that the error between the simulation results and empirical formula of shock wave peak pressure, shock wave energy are less than 6.5% and 2.1%. Therefore, the simulation results are almost in accordance with the empirical results, and the relative error can meet the practical requirement. So the simulation model based on the parameters of JWL equation of state obtained by cylinder test can accurately predict the explosion parameters of shell explosive in limited water, which is valuable for the explosive energy design of underwater weapon.