Abstract: In this study, a chemical graft of maleic anhydride (MAH) was performed onto the surface of ultra-high molecular-weight polyethylene (PE-UHMW) powders by free-radical co-polymerization, and benzoyl peroxide (BPO) was used as an initiator in this reaction. The effects of reaction time and initiator and MAH concentrations on the grafting co-polymerization were studied. The chemical properties and morphology of MAH-grafted PE-UHMW powders were investigated by ATR-FTIR, XPS, SEM and TGA. The results indicated that the MAH molecule was successfully grafted onto the surface of PE-UHMW powders, and the graft ratio and crosslinking degree of the MAH-grafted PE-UHMW increased significantly due to an increase in reaction time and initiator concentration. However, with increasing the MAH concentration, its graft ratio increased but the crosslinking degree decreased. This suggests that the increase of MAH concentration might suppress an improvement in crosslinking degree partly. A maximum graft ratio of 1.62 wt % and a maximum crosslinking degree of 69 wt % were achieved for the PE-UHMW powders.