The moleeular weight distribution of three kinds of epichlorohydrin elastomers has been studied by using a simple GPC colum．The column is packed with porous silica beads with an efficiency of more than 2000 plates per metre．It has been shown that the molecular weight distribution of the epiehlorohydrin homopolymer made by the catlyst system of i-Bu3Al-H3PO4-H2O dimethyaniline is broader than that made by the catalyst system of i-Bu3Al-H3PO4-benzothiazole sulfenamide．The polydis-persity is between the range of 3—6．The molecular weight distribution becomes narrower and the molecular weight is lowered during the milling of the elastomer．The polydispersity increased with the inc rease of conversion，the increase of mono-mer concentration，the decrease of polymerization temperature．The change of the molar ratio of dimethylaniline to the eatlyst greatly effects the polydispersity of the copolymer．