Glycidyl azido polymer (GAP) was modified with hydroxy terminated polybutadiene (HTPB) to improve the mechanical properties of GAP. Effects of different reaction conditions on mechanical properties of blend binders were discussed. Static tensile test results show synergy effect on mechanical properties of blend binders, and tensile strength and maximum elongation could reach 3.833 MPa and 593% while weight ratio of GAP and HTPB is 1:1. Tanδ-T curve from dynamic thermomechanical analysis shows single glass transition temperature near -60.2 ℃, implying that reactive compatibilization of immiscible GAP/HTPB blend binders could be got by controlling the curing reaction conditions. Micromorphology of GAP/HTPB blend binders displayed in SEM photos formed corroborating with the former two conclusions. In a word, HTPB/GAP blend binders with excellent mechanical properties possessed a good prospect for applications of GAP in composite solid propellents.