Abstract: A chemical modification was adopted to treat the surface of Kevlar fibers. The influences of the Kevlar fiber on the strength and shock resistance of cement-based composites before and after chemical modification were studied. The results indicate that chemical modification can obviously strengthen the enhancement effect of Kevlar fibers on the flexural strength and shock resistance of the cement mortar. When the fiber volume ratio is 1.0%, the flexural strength of the cement mortar reinforced by Kevlar fiber before and after chemical modification is increased by 15.18% and 23.85%, respectively, and the toughness of shock resistance is increased by 276.74% and 294.54%, respectively, compared with the reference with no fiber. The micro-morphology of Kevlar fibers and the fracture morphology of the samples were observed by SEM, and the changes of the elements on the surface of Kevlar fibers before and after modification were studied with XPS. The mechanism of Kevlar fibers in improving mortar’s mechanical performance was discussed.