Casein-pectin electrostatic complex was constructed by electrostatic adsorption, and quercetin was encapsulated in the complex to improve the stability of quercetin. Casein-pectin composites were prepared under acidic conditions. It was found that the highest transmittance was 0.81 when the concentration ratio of Casein-pectin was 1:2. Under different pH (2.0~7.0) conditions, Casein-pectin complex exhibited better stability than Casein. When the concentration of CaCl2 was 20 mg/mL, the diameter of Casein-pectin composite was the smallest, which was 346.1 nm. UV-vis curves showed that quercetin had been embedded in the Casein-pectin complex. DPPH and ABTS experiments demonstrated that quercetin showed better water-solubility and antioxidant activity (p < 0.05). The complex of Casein-quercetin-pectin showed good thermal stability (p < 0.05) when heated at 60 ℃ (pasteurization). The vitro digestion experiment indicated that Casein-quercetin-pectin had good sustained release ability.