Grinding wheel unbalance will result in vibrations of grinding machines and affect the quality and precision of workpieces. Therefore, a balancing system is necessary for grinding machines to lower the vibrations caused by unbalance. In this study, a liquid transfer active balancing system, in which the balancing liquid was forced by compressed air to transfer between opposite chambers, was applied to the high-speed grinding spindle. The requirements of gas pressure and linearity of balancing ability were analyzed to confirm the feasibility of the proposed device. In addition, an active balancing experiment was also carried out efficiently during the operation.