Side-chain alkylation of toluene with methanol was studied over cesium-modified zeolite X to produce styrene. Cesium-cation exchanged catalysts were prepared from the parent NaX（commercial Linde 13X） by ion-exchange method with various cesium acetate and nitrate solutions. And boron-added catalysts were modified with boron-added cesium acetate and nitrate solutions. Reaction products were styrene, ethylbenzene and small amount of xylene isomers. And yield and selectivity of styrene were enhanced in proportion to the concentration of the exchanged cesium solution. Acidity and acid strength of a catalyst were decreased, while basicity and base strength of a catalyst were increased slightly as the concentration of ion-exchange solutions was higher. Boron-addition resulted in great increment of styrene yield and selectivity because of considerable decrease of acidity and acid strength and a little increase of basicity and base strength. It was suggested that the increase of styrene yield requires suitable ratio of the acidity and acid strength to the basicity and base strength into the catalyst.