In order to study the energy output characteristics of three composite explosives containing Mg-based hydrogen storage materials， Ti-based hydrogen storage materials and ZrH₂ hydrogen storage materials respectively， a constant temperature detonation heat calorimeter and an underwater explosion system were used to study the detonation heat and underwater energy characteristics of the explosives. The results illustrated an order of the detonation heat in terms of a thermobaric formulation of RDX/hydrogen storage material/AP/others， which was Mg-based sample>Ti-based sample≫ZrH₂-based sample. Accordingly， the detonation heat for the three explosives were 7587.0606 kJ·kg^-1， 6416.4741 kJ·kg^-1 and 3950.6279 kJ·kg^-1. It was indicated that the detonation heat of the explosives containing hydrogen storage materials was positively correlated with the chemical potential of each hydrogen storage material. In underwater explosions， the explosion parameters including peak pressure， impulse， energy flow density and shock wave energy of the composite explosives presented a similar order， that the Mg-based sample was the best and the ZrH₂-based sample was the worst. Accordingly， the shock wave energy was 1.41 times， 1.26 times and 0.97 times of TNT equivalent for each formula. It was showed that hydrogen storage materials with much higher activity and potential energy could be beneficial for the shock wave in underwater explosion. The contribution to the energy released in underwater explosion of hydrogen storage materials was mainly in the form of bubble pulsation. The bubble energy of the composite explosives containing Mg-based， Ti-based and ZrH₂ hydrogen storage materials were 2.17 times， 1.78 times， and 0.86 times of TNT equivalent respectively， indicating that Mg-based hydrogen storage material had the best energy releasing performance in the secondary reaction， followed by Ti-based hydrogen storage material and ZrH₂was the worst The trends of the explosion parameters of the composite explosives in detonation heat test and underwater explosion test were consistent. The overall energy level of the explosives was in the order of Mg-based sample>Ti-based sample>ZrH₂-based sample. The explosive containing Mg-based hydrogen storage material had the largest energy in underwater explosion， reaching up to 2.02 times of TNT equivalent. The applicability of the ZrH₂ in thermobaric formulation was not strong for both of the energy tested in detonation heat and underwater explosion was lower than TNT.