The vapor-phase Beckmann rearrangement of cyclohexanone oxime to epsilon-caprolactam catalyzed by mesoporous molecular sieves was studied. The proton-form mesoporous molecular sieves, B-MCM-41 and H-FSM-16, exhibited extremely high activity, selectivity and stability for epsilon-caprolactam formation when 1-hexanol was used as diluent. The weak acid sites and/or surface silanol groups of mesoporous molecular sieves play an important rob in the selective epsilon-caprolactam formation.