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Resistant starch (RS) is notable for having several health benefits in humans, including glucose control and intestinal well-being. Pullulanase is able to debranch amylopectin and result in higher RS content in waxy maize starch. Different levels of pullulanase have been used to debranched waxy maize starch in the literature, but the changes of structure during debranching are unknown. In this study, waxy maize starch was cooked and debranched with 80, 160 and 240 NPUN/g starch pullulanase. One pullulanase unit (NPUN) was defined as the amount of enzyme, which, under standard conditions, hydrolyzes pullulan, liberating reducing carbohydrate with reducing power equivalent to 1 µmole glucose per minute, and crystallized at 25°C. The structure of waxy maize starch during debranching was investigated and the digestibility of the debranched products was measured. When pullulanase was increased from 80 to 240 NPUN/g, more amylopectin was debranched in same debranching time, and the degree of crystallinity and the RS content were increased. After the debranched starches were crystallized at room 25°C for 24 hours, the RS contents were greater than 63%.