Taking 1,3,5-tris(2-hydroxyethyl)-1,3,5-triazinane-2,4,6-trione as initiator,boron-trifluoride etherate as catalyst, and 2-chlorooxirane as monomer,two polymers(polyepichlorohydrin(PECH)) with different molecular weights were synthesized by the opening-ring polymerization of epichlorohydrin. And then two bran-new tri-arms glycidyl azide polymer azide(GAPA) were obtained by the reaction of nitration and azidonation. The structure of GAPA was characterized by IR and GPC. Results show that the glass transition temperature of GAPA is -52.86 ℃,and its thermal decomposition temperature is 247.9 ℃. The superior properties of GAPA show that it can be used as an energetic plasticizer.