The zeolite Y was modified by a series of potassium compounds including KNO3, K2CO3, KHCO3, KOH, and KF. The obtained microporous materials exhibited quite different structural and basic properties. Such differences can be attributed to their different guest-host interaction. These materials displayed different catalytic activity on the vapor phase methylation of cyclopentadiene with methanol. The activity is well correlated with the basicity and surface areas of catalysts.