Robust active vibration control technology is still on its way to develop, though there has been a great number of studies on active vibration control (AVC) topic published since 1980s. The key is to find a good control strategy fitting AVC use and with strong control robustness, in addition to other qualities. As a newer member of robust control strategies, variable structure control (VSC) has attracted control researchers to study its application potentiality at different engineering areas for recent years. Few of them, however, have already paid attention to use in AVC area. In this paper, VSC design methodology used for AVC of a simply-support rectangular plate is investigated. The control design process at the modal state-space is deduced and the matching conditions introduced. Numerically simulated results by using VSC under scheme of the independent modal space control are obtained and compared to those obtained by using least quadratic control and the poles allocation method. It shows that VSC has advantages over the traditional control strategies at control robustness and can control more vibratory modes. [Work supported by the Zhejiang Science and Technology plan fund, PRC.]