Graft copolymer containing reactive group and use thereof

A graft copolymer containing reactive groups and use thereof. The graft copolymer is a kind of polymer containing reactive groups and macromolecular copolymer side chains, and is copolymerized by means of radical polymerization of 20 wt% to 99 wt% of monomer A containing a carbon-carbon double bond, 0.5 wt% to 40 wt% of unsaturated monomer B containing a reactive group, and 0.5 wt% to 40 wt% of macromolecular polymer C containing carbon-carbon double bonds. The preparation process comprises the steps of: firstly, obtaining macromolecular polymer D by means of radical copolymerization, then preparing the macromolecular polymer C containing carbon-carbon double bonds by means of reaction between the groups, and finally, performing radical copolymerization of the obtained macromolecular polymer C, the monomer A and the monomer B, and obtaining the graft copolymer containing the reactive groups after drying and devolatilization. The graft copolymer containing the reactive groups can be used as a compatibilizer for blending a polymer and a glass fiber reinforced material and a chain extender for a polymer.