To improve mechanical properties of glycidyl azide polymer (GAP) elastomer, primary hydroxyl terminated GAP prepolymer (PH-GAP) has been synthesized by end-capping modification of GAP using carbamate reaction. FTIR, 13C-NMR, GPC results indicate that the functionality, molecular weight, and molecular weight distribution of PH-GAP are consistent with those of the original GAP. Mechanical tests indicate that mechanical properties of PH-GAP elastomer are much better than those of GAP elastomer. Swelling tests discover that the apparent molecular weight of the network chain in PH-GAP elastomer is much less than that of the original GAP elastomer, and PH-GAP elastomer has much perfect network structure. Network structure defect is the main factor causing inferior mechanical properties, and the GAP prepolymer terminal structure plays an outstanding role in the mechanical properties of its cross-linked elastomers. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013