Fatty acids and protein play a crucial role in reducing starch digestion. To investigate the effect of oleic acid (OA) and whey protein (WP) on the digestion of oxidized and/or hydroxypropyl starches and its mechanism, the changes on digestion, properties and microstructure of starch before and after complexation with OA and WP were analyzed using rapid viscosity analyzer (RVA), rheometer, scanning electron microscope (SEM), Fourier transformation infrared spectroscopy (FT-IR) and X-ray diffractometer (XRD). Results showed that starches with OA and WP showed cooling peaks in RVA curve due to starch-OA-WP complexes formation. Additionally, OA and WP had synergistic effects on the increase of storage modulus (G′), the decrease of gel pore size and digestion of starches. OA and WP had a greater effect on digestion of oxidized hydroxypropyl starch (OHPS) than that of hydroxypropyl starch (HPS) and oxidized starch (OS). Specifically, resistant starch content in HPS, OS and OHPS was increased by 82.41%, 58.67% and 279.18%, respectively, due to OA and WP incorporation. This was attributed to the decrease of solubility and increase of order degree of OHPS caused by OA and WP. Therefore, the appropriate hydrophilic and lipophilic properties of OHPS was helpful to complex with OA and WP.