As the poor mechanical properties of four-component hydroxy-terminated polybutadiene(HTPB) propellant(ammonium perchlorate/hexogen/Al/HTPB, AP/RDX/Al/HTPB), a modified borate ester bonding agent(BEBA) was synthesized using N, N-dihydroxyethyl-3-amino methyl propionate as the external connection monomer, polybutylene adipate(PBA) with low molecular mass as interconnection monomer, and tributyl borate as material. Polybutylene adipate(PBA) was synthesized using adipic acid and 1, 4-butanediol as materials, and N, N-dihydroxyethyl-3-amino methyl propionate was synthesized from diethanolamine and methyl acrylate. Their structures were characterized by FT-IR, GPC, ¹H NMR, and GC-MS. The application of modified BEBA as bonding agent for four-component HTPB propellant shows that with the curing parameter of 1.01, the crosslinking parameter of 0.22, and the mass ratio between BEBA and JH03 of 0.08/0.04, the mechanical properties of the four-component HTPB propellant are the best at high(70 ℃), constant(20 ℃) and low(-40 ℃) temperatures.