The side-chain alkylation of toluene with methanol catalyzed by the modified binary zeolite catalysts of KX and Al2O3, KX, KY, KM, or KZSM-5 has been studied. It was found that the selectives of styrene increased with the partial charge on the (A104) tetrahedra in the second zeolite component. The KX/KZSM-5 binary zeolite catalysts had much higher activities than did the separate zeolite catalysts, and the catalytic properties were greatly improved after H3BO3 and KOH modifications. Comparing the alkylation data with the t.p.d, measurements of NH3 and C02, Sanderson's electronegativity, and the partial charge on the(A104) tetrahedra, it is concluded that the side-chain alkylation of toluene with methanol on the binary zeolite catalysts is an acid-base cooperative, selective reaction.