The effects of different temperature-time regimes of enzymatic retrogradation on the particle size, microscopic morphology, crystal structure, functional groups and epigallocatechin-3-gallate (EGCG)-loading capacity of debranched starch nanoparticles (DBS-NPs) prepared with green banana starch were investigated. Meanwhile, the stability, antioxidant properties and in vitro release behavior of EGCG@DBS-NPs were investigated. It was shown that compared with green banana starch, the particle size of DBS-NPs decreased from (23.4 ± 7.3) μm to (208.5 ± 2.7) nm, and the crystal structure changed from type C to C→B or C→A. Besides, the relative crystallinity and the hydrogen bonding force between molecular chains were enhanced. EGCG showed the highest loading capacity (4.34%) and encapsulation efficiency (86.89%) in DBS-NP50-12, and their combination exhibited synergistic antioxidant activity. EGCG@DBS-NP50-12 was found to be more stable in a near neutral environment than in an acidic environment, and significantl more stable than free EGCG during storage. EGCG@DBS-NP50-12 exhibited excellent slow release behavior in vitro, which was fitted to a first-order kinetic equation. This study provides a reference for the preparation and application of starch nanoparticles, which has potential value in the construction of starch-based bioactive carriers.