The invention discloses a preparation method of nano compound metal sulfide adopting a core-shell structure. According to the preparation method of the nano compound metal sulfide adopting the core-shell structure, a metal sulfide A is prepared through liquid phase thermolysis, the A serves as the core, another metal ion B is attached to the surface of the A through ion exchange, and a nano compound metal sulfide A@B adopting the core-shell structure is obtained. The preparation method is simple to operate and environment-friendly, and the core-shell compound metal sulfide with uniform nanoparticles ranging from 10 nm to 20 nm and controllable size, morphology and atom proportion is obtained; the metal sulfide can absorb ultraviolet light and visible light effectively and plays a significant role in degrading organic pollutant Rhodamine B and methylene blue; compounding of photo-induced electrons and holes is effectively prevented, and the photocatalysis efficiency of the metal sulfide is improved.