An energetic binder was synthesized through ring opening copolymerization of glycidyl nitrate (GLYN) with polycaprolactone (PCL) as a macroinitiator to form tri-block copolymer PGN-PCL-PGN. Effect of monomer concentration, catalyst, reaction time and solvent was investigated in polymerization. Resulting tri-block copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The DSC result shows that glass transition temperature of tri-block copolymer (T-g=-56.2 degrees C) is lower than PGN (T-g=-35 degrees C). In optimal condition, the M-w of this polymer was obtained 2900g/mol.