Thermal behaviour of polyglycolic acid in melt polymerization of glycolide was investigated as a function of lauryl alcohol content. There were showed three endothermic peaks such as glycolide melting peak, lower molecular weight melting (oligomer) peak and higher molecular weight melting peak at early stage on glycolide melt polymerization under lauryl alcohol. But there were showed only two peaks, glycoside melting peak and lower molecular weight melting peak without laurel alcohol. Conversion increased slowly with the reaction time up to 50 minutes, and then gave a sudden increase above that. The reaction time to disappear in glycolide melting peak during polymerization was shortened with the increase of lauryl alcohol content. Zero-shear viscosity of polyglycolic acid decreased with the increase of free acid content in glycolide.