The problem of cleaning water from toxic compounds has recently become more and more urgent. antibiotics, dyes and other hard-to-oxidize organic compounds content is increasing in industrial and municipal wastewater, which traditional water treatment methods cannot fully remove. One of the most promising and environmentally friendly water purification methods is organic compounds photocatalytic decomposition under the light influence in the presence of semiconductor materials. This paper presents the results of studies of the of chemically deposited CuS and CuS (Ni) films catalytic activity in methylene blue photodegradation reaction. For targeted copper sulfide films chemical deposition, ionic equilibria were analyzed in the system «CuSO4 - CH3COONa - CH3COOH - N2H4CS» and predominant copper(II) complex compounds in the solution were determined in the pH range 0-14, the potential copper(II) sulfide formation area by a homogeneous mechanism has also been established. CuS films with a thickness of 100±10 nm with good adhesion to the surface of both sitall and matted quartz were obtained by chemical bath deposition. Electron microscopic surface studies of CuS films deposited on sitall substrates have shown that the particles from which they are formed have an average size of ~10 nm. It is shown that methylene blue dye decomposition degree on CuS thin film photocatalyst surface under visible light influence is 15.6%.