Abstract: 2-Hydroxy-3-butoxypropyl starches (HBPS) were synthesized by environmentally friendly process using butyl glycidyl ether(BGE) as hydrophobic reagent, water as solvent and sodium hydroxide as a catalyst. The reaction conditions were investigated and optimized. Optimum conditions were obtained as follows: n(BGE):n(AGU)=0.615, amount of solvent was m(H2O):m(AGU)=2:1, amount of catalytical NaOH was n(NaOH):n(AGU)=0.5:1, reaction time was 5h, reaction temperature was 75 ℃, molar substitution (MS) of 2-hydroxy-3-butoxypropyl was up to 0.45, the reaction efficiency(RE) was 73%. The HBPS and corn starch were characterized by IR, 1H-NMR and 13C-NMR. In addition, the TG result indicates that hydrophobic modification can improve the thermal stability of stach .