Acetic acid dehydration was performed over surface-modified MCM-41. The catalyst was prepared by silylation of MCM-41 followed by calcination. The surface-modified MCM-41 had silanol groups as the active sites for acetic acid dehydration. The actalytic activity was increased as the increase of the degree of surface-modification. Surface-Modification increased the wall thickness of MCM-41, resulting in the increase of hydrothermal stability of the catalyst as well as the optimization of the quantity of silanol group needed for acetic acid dehydration.