In this study, flower molybdenum disulfide (MoS2) was surface-modified with polyethyleneimine(PEI) to prepare PEI/MoS2 composite adsorbents for Cr(VI) enrichment in aqueous solution. The physicochemical properties of PEI/MoS2 were characterized by SEM, TEM, XRD, FTIR, BET and XPS methods. The influences of PEI loading, solution pH, contact time, adsorption temperature, and initial Cr(VI) ion concentration on the adsorption performance of PEI/MoS2 for Cr(VI) were investigated. Under the optimal conditions, and the initial Cr(VI) ion concentration is 50 mg L− 1, the adsorption capacity of PEI/MoS2 is 120.7 mg g− 1. The adsorption rate is fast, equilibrium time is 6 h. Competitive adsorption studies of the Cr(VI), Co(II), Zn(II) and Cd(II) quaternion system were also investigated, the results indicated that selectively adsorbed amount of Cr(VI) on PEI/MoS2 is significantly higher than that of Co(II), Zn(II) and Cd(II) ions. The adsorption process was spontaneous and conformed to Freundlich isotherm and pseudo-second kinetic model. The consecutive adsorption-desorption experiments indicated that the PEI/MoS2 has excellent reusability.