The invention relates to a method for reducing rotor-stator interaction of a pump turbine and plant vibration. The method is characterized by comprising the optimization of the flowing two aspects for the pump turbine: 1) the relation between the number Zr of runner blades of the pump turbine and the number Zg of movable guide vanes is optimized so that the number Zg of the movable guide vanes is not an integer multiple of the number Zr of the runner blades, namely, Zg/Zr is not equal to an integer, and the ratio of the number of the movable guide vanes to the number of the runner blades is close to 1.5, 2.5, 3.5 and the like as far as possible; and 2) the ratio D0/D1 of the distribution diameter Do of the movable guide vanes to the diameter D1 of the high-pressure side of a runner is increased to more than 1.165, namely, the distance between the movable guide vanes and the high-pressure side of the runner is increased. The method is formed on the basis that the principle and the hazard mode of the rotor-stator interaction between the runner blades and the movable guide vanes of the pump turbine are found out, the problem can be solved starting from the design of the pump turbine, and the fundamental problem can be solved.