Abstract: At temperatures below 100 ℃, granular integrity can be retained by most starches with different swelling power. To investigate the hydrolysis behavior of β-amylase on different crystal types of expanded starch, expanded starch was prepared from waxy corn starch (A-type crystal) and potato starch (B-type crystal), and the effects of β-amylase on the hydrolysis rate, viscosity, apparent morphology, thermodynamic properties, crystallization characteristics, and molecular structure of expanded starch were explored. The results showed that β-amylase utilized the surface pores of waxy corn starch for enzymatic hydrolysis and formed pits on the surface of potato starch. Before enzymatic hydrolysis, swollen potato starch exhibited higher swelling power and viscosity. The hydrolysis rate of swollen potato starch (84.28%) by β-amylase was higher than that of swollen waxy corn starch. Differential scanning calorimetry (DSC) results showed that after hydrolysis by β-amylase above the gelatinization temperature, the thermal enthalpy (ΔH) of both crystalline types of swollen starches increased, indicating that the enzymatic products were more prone to forming double helical structures. Additionally, it was revealed by X-ray diffraction (XRD) results that the crystalline types of the two swollen starches were not altered by enzymatic hydrolysis, but their relative crystallinity was increased, suggesting that the crystalline structures became more compact after enzymatic hydrolysis. At the same time, the degree of branching of waxy corn expanded starch and potato expanded starch was significantly increased after enzymatic hydrolysis, from 16.51% and 13.68% to 23.08% and 30.47%, respectively. It was demonstrated by these results that a significant hydrolytic effect was exerted by β-amylase on both swollen starches, with notable differences observed between different crystalline types.