The crude alginate lyase was made by acetone purification from abalone intestine and its activity was determined as 46.8U/mg.Sodium alginate was then lysed by the crude alginate lyase extracted.The hydrolysate produced was isolated into three fractions after enzymatic hydrolyzing,which were fraction of high mannuronic acid oligosacchride,fraction of high guluronic acid oligosacchride and the mixture of mannuronic acid and guluronic acid oligosacchride.The hydrolyzing time and amounts of lyase added were taken as variables for degradation.The result showed that the amount of three fractions of oligosacchrides isolated increased with the increases of lyase concentration added,while the polymerizations of the oligosacchrides produced were irrespective with the concentration of alginate lyase added.