This paper presents an active balancing method to reduce the imbalance-induced vibration of rotating machinery. In this method, the rotor was modeled by influence coefficient and a gain scheduling strategy was proposed to suppress the imbalance-induced vibration during acceleration. Besides the theoretical derivation of this active balancing algorithm, a comprehensive testbed was built to validate this scheme. The validation results were presented. To apply an active balancing scheme, the axial position of the actuator needs to be determined. This paper also presents an optimal balance plane selection procedure. A numerical study shows the effectiveness of this selection method.