Abstract Dissipative particle dynamics and molecular simulations were carried out to investigate the phase behaviors of glycidyl azide polymer (GAP)/hydroxyl-terminated polybutadiene (HTPB) polymer blend in dioctyl sebacate (DOS), and mixture of DOS and bis(2,2-dinitropropyl)formal/acetal (A3), respectively. The rheology of GAP/HTPB propellant slurry plasticized by A3/DOS was studied. First, single-phase aggregations of GAP and HTPB appear slightly in A3/DOS whereas it is conspicuous in DOS, which results from the small surface tension between the GAP/HTPB plasticized by A3/DOS and the weak thermal diffusion of this blend. Furthermore, with the plasticizing ratio (po/pl) increasing to 1.2, the GAP/HTPB propellant slurry plasticized by A3/DOS exhibits small viscosity and yield stress, and the Newtonian-like behavior of slurry improves its manufacturability. Finally, integral GAP/HTPB-based propellant can be obtained using A3/DOS as plasticizers.