Ductility of fiber reinforced cement-based materials is closely related to the interfacial bond of fiber/matrix, especially for the fiber with surface chemical inertness. In this study, graphene oxide (GO) was coated on polyethylene (PE) fiber to strengthen its bond to matrix. Firstly, the effect of PE fiber with and without GO coating on the microstructure and tensile properties of cement mortar was investigated. Compared with PE-Mortar, GO/PE-Mortar showed a significant enhancement in first cracking strength, ultimate tensile strength and strain by 11.7%, 46.3% and 70.4%, respectively. The hydrogen at honeycomb lattice of GO and oxygen in the hydroxyl and epoxy of GO can interact with oxygen in calcium silicate hydrogen (C–S–H) and hydrogen in PE chains via intermolecular H-bonding, contributing to strengthen the bond of PE fiber/matrix. Secondly, the molecular dynamics (MD) simulation results revealed that the atomic translational motion across the interface of C–S–H/PE was decreased after the coating of GO, and the whole system was thus becoming more stable. Moreover, in the pull-out simulation, the maximum force for PE fiber to be pulled out from the C–S–H structure was increased by 41.67%, because GO helped to turn the weak C–S–H/PE interface to be that with a higher interfacial bonding energy at the C–S–H/GO and GO/PE interfaces. In conclusion, GO, as a promising coupling material, has great potential to strengthen the interfacial bond between the PE fiber and cement matrix, to develop cement-based materials with enhanced ductile properties.