The inherent poor stability of CsPbBr₃ perovskite quantum dots (QDs) is the main impediment restricting their applications. In this work, a CsPbBr₃@TiO₂ core-shell structure nanocomposite with high water stability and efficient photocatalytic activity was fabricated through the hydrolysis of tetrabutyl titanate, followed by calcination. The as-prepared CsPbBr₃ QDs have a size of ca. 8 nm, encapsulated by incompletely crystallized TiO₂ protective layer with a thickness of ca. 20 nm. The photocatalytic performance of the CsPbBr₃@TiO₂ nanocomposite was investigated by degradation of Rhodamine B (RhB) in water under visible light irradiation. The result shows that the CsPbBr₃@TiO₂ nanocomposite exhibits much more enhanced photocatalytic activity than pure TiO₂ and CsPbBr₃ perovskite quantum dots. The photocurrent test results showed that the formation of the CsPbBr₃@TiO₂ heterostructure can promote the separation of photogenerated carriers, which led to the improvement of photocatalytic performance of the composite material. More importantly, TiO₂ can act as a protective layer to separate CsPbBr₃ from water, which brings about the high water stability of the CsPbBr₃@TiO₂ nanocomposite. After photocatalytic degradation of pollutants, the recovered CsPbBr₃@TiO₂ nanocomposite retained its original morphology, luminescent and photocatalytic properties.