Objective To investigate the effect of microwave treatment on the structure, physicochemical, and digestibility of oat starch.Methods Oat starch (OAT) is taken as the research object to analyze the effects of different microwave treatment times on the particle size distribution, microstructure, crystalline structure, short-range ordered structure, thermodynamics, rheology, and digestibility of OAT.Results With the prolongation of microwave treatment time, OAT granules are expanded, and the particle size is significantly increased. Additionally, the crystallinity is decreased from 12.32% to 5.33%, the infrared absorption ratio R1 047 cm-1/1 022 cm-1 is decreased from 0.73 to 0.62, and the half width peak of the Raman spectrum at 480 cm^-1 is increased from 15.94 to 20.16. The short-range orderliness is decreased. For physicochemical properties, the water absorption index, cold water solubility, and swelling degree of OAT are significantly increased, while viscosity and breakdown value are significantly decreased. The enthalpy value ΔH is decreased from 7.71 J/g to 0. For digestibility, as the microwave treatment time is increased, the rapid digestible starch (RDS) content is gradually increased, while the slow digestible starch (SDS) and resistant starch (RS) content is gradually decreased.Conclusion Microwave treatment can improve the physicochemical properties and digestibility of OAT.