Abstract: The object of the study was to determine the optimal conditions of receptor reaction catalyzed by alternansucrase, a new kind of glucansucrases, to produce oligosaccharide DP4.Leuconostoc corium SK24.002 was used as the culture to produce alternansucrase, and receptor reaction of alternansucrase was conducted using sucrose and maltose as substrates. Results showed that the optimal conditions of receptor reaction catalyzed by alternansucrase were: 100 g / L sucrose + 100 g / L maltose + 0.3U / m L enzyme solution in 40℃ in 50 mmol / L p H5.4acetate buffer for 5h.Under these conditions, the maximum yield of oligosaccharide DP4 finally achieved 52.8g / L.The products of receptor reaction catalyzed by alternansucrase can be greatly impacted by the reaction conditions.