Waste water treatment with adsorbents has become one of the most effective methods. In this work, we have reported the preparation of the flower-like Cu2MoS4/g-C3N4 composites. The Cu2MoS4 nanosheets were arranged in a flower-like structure by a simple one-step hydrothermal synthesis method and attached to g-C3N4 nanosheets. The as-prepared flower-like Cu2MoS4/g-C3N4 composites was found to have potential for the adsorption of RhB in aqueous solution. The microstructure of the product was analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscope (XPS), transmission electron mi- croscopy (TEM), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and BrunauerEmmett-Teller (BET). The effects of the ratio of the composite material, the initial concentration of the dye and the contact time were explored. The Langmuir maximum adsorption capacity of the flower-like Cu2MOS4/g-C3N4 composites for RhB was reached 420.2  mg/g. Moreover, the adsorption process is consistent with the pseudo second-order kinetic model, the Langmuir isotherms model and the Freundlich isotherms model.