Ulansuhai nur is located in the cold and dry area of China, and the management of heavy metals in the sediments is related to water safety in the lower places of the Yellow River. Graphene oxide (GO) is modified to obtain magnetic graphene oxide (G-F) and chitosan grafted graphene oxide (G-N-C) materials, which are used to immobilize Cu in the sediments. The modified materials are characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffractometer (XRD). G-F respectively reduces the concentration of Cu in the overlying and interstitial water by 61.5-66.3% and 22.4-47.1%, which is more effective than GO and G-N-C. Experiments are designed to determine the effect of phosphates concentration on immobilizing Cu in the sediments by modified materials. The results show that a low concentration of phosphates solution is beneficial to the immobilization of Cu in the sediments, and the capability of G-F to immobilize Cu is higher than that of GO and G-N-C. G-F presents a lower increase in organic phosphorus in the sediments than GO and G-N-C. In summary, the modified materials can immobilize Cu in the sediments, potentially reduce the water body eutrophication, and improve the lake ecological environment.