Fly ash (FA), a solid waste product from thermal power stations, can be served as a nonreinforcing filler for polymers. Due to the lack of hydroxyl groups of FA, it is infeasible to prepare polymer composites with excellent properties by coupling agents. In this work, high performance nitrile butadiene rubber (NBR)/FA composites were prepared by designing a surficial immobility layer. First, the carboxyl group of sorbic acid (SA) undergoes interfacial acid-base neutralization reaction with metals oxide of FA to form ionic bonds. Second, the double bonds of SA can graft to NBR molecular chains with the assistance of a peroxide initiator. Consequently, 500% modulus and tensile strength of NBR/30FA/8SA composites are higher than those of NBR/30FA composite by 213.8% and 125.9%, respectively, which makes FA changing from the nonreinforcing filler to reinforcing filler and provides a new way for the large-scale utilization of FA in the polymer industry.