Cu₂ZnSnS₄ has good photocatalytic application prospects due to its high absorption coefficient in a visible light range and high carrier mobility, but the limited photocatalytic activity and catalytic stability restricts its practical applications. Cu₂ZnSnS₄ nanomaterial was prepared by a hydrothermal method with zinc chloride, tin chloride, copper chloride and thiourea as precursors, and PEG400 and OP10 as surfactants. The microstructure of the as-prepared Cu₂ZnSnS₄ nanomaterial was characterized and the influence of surfactant on the optical band gap and the photocatalytic degradation performance of the samples was determined by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy, respectively. The results show that three kinds of Cu₂ZnSnS₄ materials prepared all have a kesterite micro-phase, and the addition of PEG400 and OP10 into the precursor results in the variation of the microstructure, stoichiometric ratio and optical band gap of the materials, consequently determining their photocatalytic properties. After methylene blue degradation for 50 min, Cu₂ZnSnS₄ nano-powder synthesized with PEG400 has an optimum photocatalytic degradation rate (i.e., 95.7%). It is indicated that the photocatalytic activity and stability of Cu₂ZnSnS₄ nanomaterials can be improved by reducing the optical bandgap and enhancing the crystallinity, thus paving a promising approach to improve its photocatalytic performance.