Abstract: The waterborne polyurethane prepolymer (WPUP) encapsulated ZnO particles(ZnO@WPUP) were synthesized by using in-situ emulsion polymerization method. The aramid fibers pretreated by KOH were then secondly treated by modified ZnO emulsion. In addition, aramid/rubber composites modified by ZnO@WPUP were obtained by the vulcanization between aramid fiber and nature rubber.Meanwhile, the influence of ZnO@WPUP on the adhesion property of aramid/rubber composites was analyzed by FTIR, SEM and cord-H-pull test. The results show that WPUP can effectively enhance the dispersing property of ZnO. The roughness and dispersing property of ZnO@WPUP on the surface of aramid fibers increase obviously as the content of WPUP increasing. Thereby the modified ZnO can effectively improve the amount of adhesive rubber on the aramid fibers surface, and the adhesion strength of aramid/rubber composites is enhanced significantly.