This paper focused on the effect of amylomaltase( 4αGT) modification on the normal corn starch including the branch chain length distribution and slow digestion property with different enzyme concentration. The results showed a decreased MW and amylose content,and an increased SDS content in the contrary with the increase of enzyme concentration. Compared to the normal corn starch,the modified starch using 4αGT for 20 U/g starch increased the SDS from 9. 40 % to 21. 68 %,decreased the amylose content from 32. 8 % to 25. 3 % and also showed a lower molecular weight. The chain length distribution of 4αGT-treated starch showed an increased amount of short( DP <13) and long( DP >30) chains. All these results suggested that starch treated with partial 4αGT synthesized novel amylopectin clusters containing slow digestibility.