A growing increase in fly ash (FA) becomes a serious problem for environmental protection. In order to alleviate this problem, many people have tried to use FA to prepare polymer composites. However, due to the lack of hydroxyl groups on the surface of FA, the conventional surface treatment method for FA, such as silane or titanate coupling agent modification, is unacceptable and application of FA in the polymer industry is still a huge challenge. In this work, in-situ grafting-neutralization reaction takes place within styrene butadiene rubber/FA/sorbic acid (SBR/FA/SA) composites during the vulcanization process. Experimental data show an immobilized rubber layer is established on the surface of FA, which originates from strong interactions among SBR, FA and SA. As a consequence, the tensile strength of SBR/FA/15SA composite is about 215% higher than that of SBR/FA composite, along with larger elongation at break and modulus, which suggests stronger reinforcing effect of FA/SA for SBR composites and opens a new road to use FA in the polymer industry.