The phase-transfer catalytic epoxidation of hydroxyl-terminated polybutadiene (HTPB) by hydrogen peroxide was investigated by using quaternary ammonium salts, ammonium tungstate hydrate and phosphoric acid as the phase-transfer catalyst and cocatalysts, respectively. The influences of quaternary ammonium salts, the amount of Aliquat 336 and hydrogen peroxide, the molar ratio of phosphoric acid to ammonium tungstate hydrate (PO43-/WO42-), pH value and organic solvents on the conversion of double bonds in HTPB polymer were studied in detail. The kinetic of epoxidation of HTPB was also discussed and the apparent activated energy for epoxidation of HTPB was estimated to be 21.04 kJ/mol. (C) 2009 Published by Elsevier B.V.