A combined theoretical and experimental study shows that it is possible to controlthe vibration of a flexible rotor by varying the support stiffness. The over-all rotor support stiffness can be tended to enable the rotor critical speed to shift desirably and to make good matching between the rotor and the support.A new construction of the pedestal with changeable stiffness is presened. Its stiffness can be changed continuously by changing the oil pressure which is exestedon the support by a special hydraulic system. A method for calculation of the pedestal stiffness is introduced. A microcomputer is used to control the vibrationof the flexible rotor according to the vibration signal of eddy current sensors.The controlling program uses the step approximation method. The results of the experiments are also given in this paper.