The invention discloses a radial vibration active control system and method for a rotating shaft. In the rotating shaft radial vibration active control system, an acceleration sensor is fixedly connected with a rotating shaft to be actively controlled so as to measure a vibration signal of the rotating shaft in real time; a first conducting ring is fixedly connected with the rotating shaft and iselectrically connected with the acceleration sensor; an elastic element is fixedly connected with the rotating shaft; an actuator is fixedly connected with the elastic element, so an applied acting force acts on the rotating shaft through the elastic element; a controller is electrically connected with the first conducting ring and a second conducting ring, responds to the vibration signals, analyzes and processes the vibration signals to form control signals and responds to the control signals, and the actuator applies an acting force to the rotating shaft through the elastic element so as toactively control the radial vibration of the rotating shaft.