Abstract: In order to suppress voltage fluctuation, compensate three phase unbalance, improve power factor and decrease the capacitance of static var compensator (SVC) simultaneously, an integrated control method with instantaneous reactive power theory and voltage control based on piecewise voltage-current characteristic is put forward. Fast calculation based on instantaneous reactive power theory enhances the response speed of SVC, and voltage control based on piecewise voltagecurrent characteristic ensures the good stable characteristic and expands the compensation range of SVC, which are combined by expert rules to control the compensatory reactive power. It not only increases the response speed and expands the control range, but decreases the installed capacity and operation loss of SVC. The system is put into operation in the rolling mill system of LengShuiJiang 950 mm steel plant. The effectiveness and feasibility are proved.