Abstract: Active control method for the vibration reduction of flexible cantilever beam is investigated in this paper. The independent modal space control method is used as control strategy, in which modal control law is designed using discrete-time variable-structure control method. Extraction of modal variables from actual measurements and transformation of actual control forces from modal control forces are discussed. Determination methods of discrete-time switching surface and variable-structure modal control law are presented. Effectiveness of the proposed control method is verified through a numerical simulation in the end of this paper.