Abstract: To improve the stability and encapsulation efficiency (EE) of whey protein concentrate (WPC) microcapsules, cinnamaldehyde (CA) was used to modify the interface of WPC stablized microcapsules. To optimize the preparation process of microcapsules, the particle size, EE, water content, solubility and microstructure were evaluated, and the effect of CA addition on the quality of WPC microcapsules was also assessed. The results indicated that when the WPC concentration was 5% and the oil phase content was 5%, the EE of WPC microcapsules with 1% CA was the highest, up to 92.12%, while the EE of microcapsules without CA was only 55.68%. CA addition made the microcapsule particles more plump and smooth. And the surface of microcapsules became dense and smooth. At the same time, the addition of CA was beneficial to improve the EE of low-oil content microcapsules and stabilize the EE of high-oil content microcapsules. To a certain extent, CA slightly improved the dissolution characteristics of high-oil content microcapsules. This research provided information for the development of protein microcapsules and related functional products.