Methyl 3-hydroxypropanoate was synthesized by hydroesteri- fication of ethylene oxide with carbon monoxide in the presence of Co2(CO)8 catalyst and methanol solvent. The influences of different ligands, catalyst/ligand molar ratio，reaction temperature, CO pressure, and methanol dosage in the system on the reaction were investigated. The results revealed that imidazole was a good ligand for the reaction and the optimal reaction conditions were catalyst/ ligand molar ratio1:1.5, reaction temperature 75℃, CO pressure 6.0MPa, methanol/(ethylene oxide) volume ratio 5:1. Under the optimal conditions, the conversion of ethylene oxide was 92.24%, the yield of methyl 3-hydroxypropanoate was 84.35%.