Branched glycidyl azide polymer (B-GAP) was obtained at 100 ℃，using poly epoxy chloropropane,sodium azide,and sodium hydroxide as reactants and glycol as initiator. B-GAP was transformed to branched glycidyl azide polymer nitrate (B-GAPN) with concentrated nitric acid at -20-0 ℃. Reaction parameters were used to controll molecular weight and hydroxy number of B-GAP,and moecular weight of B-GAPN. The preparation product B-GAPN is testified by infrared spectrum analysis which indicates evident decrease of hydroxy group and emergence of nitrate peak.