To investigate the influences of aluminum size and content on the performance of aluminized explosives in confined space, experiments were conducted in a fully confined chamber. Two kinds of RDX based explosives with different aluminum oxygen ratio(0.45 and 0.99) containing aluminum of 50 nm, 5 μm and 50 μm respectively were used. The data processing method of multipoints averaging for gaining quasic-static pressure and exponential decay similar for gaining the attenuation factor of pressure were proposed. Three characteristic quantities, quasic-static pressure (p_QS), rising time of pressure (t_QS) and attenuation factor of pressure (ω), were used to characterize the energy release from aluminized explosives in chamber. Results show that for the formulation with aluminum oxygen ratio of 0.45, the p_QS of sample with 50 μm aluminum powder is 0.3% and 0.7% higher than those with 5 μm and 50 nm aluminum, respectively. For the formulation with aluminum oxygen ratio of 0.99, the p_QS of sample containing 50 μm aluminum powder was 31.2% and 31.9% higher than those containing 5 μm and 50 nm aluminum powder, respectively, and the p_QS of two samples with aluminum oxygen ratio of 0.45 containing the same particle size aluminum powder are larger than the sample with aluminum oxygen ratio of 0.45. With respect to either samples containing the same size of aluminum, with the increase of aluminum oxygen ratio, p_QS increased, t_QS and ω decreased.