Functional monomers, maleic anhydride (MAH) and vinyl acetate (VAc), were used as comonomers in the solid-phase grafting of polypropylene (PP). Quantitative determination of the graft level of both MAH and VAc performed by titration and FTIR methods allowed for a good appreciation of the interaction of MAH and VAc. A product with high-graft level of both VAc and MAH was obtained when the feeding molar ratio of MAH/VAc approached 1:1. The melt flow rate (MFR) of the grafted PP decreased with the increase in the feeding amount of VAc. It was proposed that MAH and VAc molecules could form a kind of stable transition state during the graft polymerization and that the reactivity of both monomers were enhanced. The resulting multifunctional PP offers possibility for the development of novel PP-based polymer blends and composites, thus extending the application field of PP.