<p>Flavonoids in dried sea buckthorn pomace (SBP) have excellent pharmacological activity, however, their instability and low water solubility limit their application in the food and pharmaceutical industries. Protein‒oligosaccharide Maillard-type conjugates have potential as novel delivery systems for encapsulating flavonoids to improve this restriction. In this study, different types of proteins, including soy protein isolate (SPI), whey protein isolate (WPI) and gelatin (GE) conjugated with xylo-oligosaccharide (XOS) via the wet-heating Maillard reaction, and Maillard reaction products (MRPs) were used to encapsulate flavonoids extracted from dried sea buckthorn pomace. The results of the degree of grafting and Fourier transform infrared (FTIR) spectra confirmed that the MRPs were successfully prepared. The MRPs were subsequently used as wall material to prepare flavonoid microcapsules by freeze-drying. The encapsulation efficiency of the microcapsules ranged from 82.21 to 90.94%. Scanning electron microscopy (SEM) revealed that the microcapsules formed irregular glassy structures. Thermogravimetric analysis (TGA) indicated that the prepared microcapsules had good thermal stability. The water solubility of the flavonoid microcapsules (89.68–91.84&#xa0;g/L) was significantly greater than that of the free extract (55.33&#xa0;g/L). Furthermore, in vitro simulated digestion experiments revealed that the total flavonoid content (TFC) released during stomach-phase digestion was lower than that of the free extract, and the bioaccessibility of the flavonoid microcapsules improved to 64.80–78.98%, which was considerably greater than that of the free extract (28.97%). Overall, the results of this research indicated that MRPs can be used as a new type of wall material to encapsulate flavonoids and that microencapsulation may effectively increase the bioavailability of flavonoids and their application potential.</p>