Corn starch,cassava starch and amylomaize were utilized to produce cycloamylose in this study. These three substrates were debranched by isoamylase first. Then they were treated with 4-α-glucanotransferase to produce cycloamylose. The results indicated that after debranching,the maximum conversion yield of cycloamylose from corn starch increased from 20. 3% to 33. 6%( 1. 7 folds); the maximum conversion yield of cycloamylose from cassava starch increased from 16. 82% to 32. 4%( 1. 9 folds); the maximum conversion yield of cycloamylose from amylomaize increased from 24. 53% to 44. 07%( 1. 8 folds). Therefore,it was an efficient method to produce cycloamylose by combined treatment of isoamylase and 4-α-glucanotransferase. The study also showed the method has a great potential in the industrial scale.