To improve the wettability and adhesion, graft polymerization of acrylamide (AAm) and glycidyl methacrylate (GMA) was performed onto the surface of ultra-high modulus polyethylene (UHMPE) fiber pretreated with Ar plasma. Following the plasma treatment and the subsequent exposure to air to introduce peroxides onto the fiber surface, graft polymerization onto the UHMPE fiber was allowed to proceed from the polymer peroxides either in deaerated monomer solution at an elevated temperature (degassing method), or in aerated monomer solution containing riboflavin at 30-degrees-C under UV irradiation (photoinduction method). The monomer solution was prepared from water and dioxane for AAm and GMA, respectively. After rigorous removal of homopolymers, surface analysis of the grafted fibers was performed with ATR-FTIR and XPS, which revealed that PAAm and PGMA chains were grafted in the surface region of fibers. The grafting rate of PAAm by the photoinduction method was much higher than that by the degassing method when compared at the same concentration of the AAm solution. The amount of PGMA grafted was greatly affected by UV irradiation time, but depended on plasma treatment time to an insignificant extent if the treatment was carried out for longer than 30 s. Reaction of propylamine with the PGMA-grafted surface resulted in the appearance of a nitrogen peak in the XPS spectrum, suggesting the presence of epoxy groups on the surface of PGMA grafted fiber.