Based on the fact that the unbalance vector of the thin-disk part with large diameter–thickness ratio can be regarded as distributed in one face, the measuring and calculating methods for the unbalancing vector of thindisc workpiece are proposed according to the vibration change of machine tool spindle before and after the workpiece is clamped. Based on the extra unbalance vibration measuring system, the functions of spindle exact stop, tool positioning and weight moving control of composite numerical control machine tools, the concept of online weight moving correction for the unbalance thin-disk workpieces is proposed. The feasibility of unbalance vector online measurement and correction for thin-disc workpiece is verified by experiments in the paper. The research can be used to online measure and correct of the unbalance thin-disk workpiece without dynamic balancing machine, and it has certain reference value in saving workpiece balance costs, improving workpiece balance efficiency and machining accuracy.