Due to simple structure and lack of large side groups or branched chains, polyethylene (PE) fibers have disadvantages such as poor creep resistance, which limits their application in various fields. Modified polyethylene fibers with different contents of dicumyl peroxide (DCP) by melting spinning were prepared. The effect of DCP content on the properties of modified polyethylene fibers was studied. The results indicate that the addition of DCP leads to varying degrees of cross-linking of polyethylene molecular chains, resulting in decreasing of the melting point and crystallinity of crosslinked polyethylene fibers, with minimal changes in crystal structure and grain size. Compared to uncross-linked polyethylene fibers, the fracture strength and modulus of crosslinked polyethylene fibers with 2% DCP content are increased by 9.2% and 50.4%, respectively, while the elongation at break is decreased by 78.0%. In addition, with the increase of DCP content, the creep resistance of modified LDPE fibers gradually improves. The creep elongation of LDPE fibers cross-linked with 2% DCP is decreased by 50.0%. Using DCP as crosslinking agent, polyethylene fiber molecular chains are chemically crosslinked to form a cross-linked structure, which reducing the slip between molecular chains and achieving the goal of creep resistance.