Abstract: As a new resource food additive, ω-3 fish oil powder has been widely used in various foods and beverages including infant foods. This has a far-reaching significance for Chinese consumers whose diets generally lack DHA and EPA intake. In this work, natural Quillaja saponin (QS) was used to stabilize the fish oil emulsion based on its self-assembly characteristics at oil-water interface. With the spray-drying technology, fish oil powder was prepared with a high-oil-loading of 76.76%. And then, the characterization of fish oil powder with different amounts of QS was further investigated including encapsulation features, oxidation stability, reconstitution, and the physical stability under different environmental stresses. The results showed that fish oil powder with a high encapsulation rate of 90.24% was produced and the encapsulation rate was positively related to QS content. Compared with traditional casein-encapsulated fish oil powder, QS-encapsulated fish oil powder has higher oxidation stability, which was significantly inhibited with the increase of QS addition. Moreover, the QS-encapsulated fish oil powder showed a good reconstitution ability and stability under extreme environmental conditions, e.g., heating (100 ℃, 30 min), salt ion (500 mmol/L) and pH (pH 3-11). Therefore, the self-assembly of QS at oil-water interface could improve the encapsulation and oxidation properties, provide good reconstitution and stability under extreme conditions, supporting the pulverization of oil.