To enhance removal of hexavalent chromium Cr(VI), peanut shell (PS) was modified by polyethyleneimine (PEI) and modified peanut shell (MPS) was obtained. MPS was characterized and the results indicated the success of modification. The batch and column modes were performed to study the adsorption property. It was in favor of Cr(VI) adsorption at acidic solution and the existence of common salts was not conducive. Electrostatic attraction was the major mechanism. The adsorption quantity toward Cr(VI) was up to 42.5 mg·g−1 at 293 K from experiments. Pseudo-second order model and Elovich model can predict kinetic process. Langmuir model and Freundlich model had great consistency with isotherm curves. Yan model and Clark model have better agreement with Cr(VI) adsorption in fixed-bed column. There was some characteristic of reuse for spent materials. It was concluded that MPS can availably eliminate Cr(VI) in wastewater and improve the utilization of PS in waste treatment.