A method to design a nanoparticle using bovine serum albumin and flavonoid was introduced in this work. Kaempferol and rutin were used here as models of hydrophobic flavonoids. Bovine serumalbumin molecules formed nanoparticle with diameter of X–30 nm, promoted by dimethyl sulfoxide and flavonoid. The adsorption of kaempferol or rutin on bovine serum albumin was mainly hydrophobic, particularly happened in the region of tryptophan residue of the protein, and promoted the formation of a hydrophobic core surrounded by hydrophilic outer layer. One bovine serum albumin molecule could load at least 12 kaempferol or 5 rutin molecules. The controlled-releasing measurements showed that the bovine serum albumin nanocarrier has a long-term protection effect on the stability of kaempferol and rutin in the neutral aqueous medium. Moreover, the antioxidant activity evaluation indicated that the activities of kaempferol and rutin were not hindered by the embedding of bovine serum albumin nanoparticle.