Abstract: Fine structure of slowly digestible starch (SDS) formed during dual-enzymes treatment was investigated. Through the hydrolysis of β-amylase and transglycosylation of transglucosidase, higher amount of SDS could be obtained. The result indicated that the chain length distribution, iodine binding and digestibility of starch samples, which were subjected to different time of transglycosylation following β-hydrolysis, changed obviously. After maize starch being treated by β -amylase for 4h, the highest SDS amount of 13.95% was gained when transglucosidase continued to treat for 24h, the average chain length was 12.58, and branch density was 7.95% . The experiment proved that dual -enzymes treatment could improve the digestibility of maize starch effectively.