To solve the problem of positioning accuracy for the circular workpiece in the steel ring set under the CNC machine tool, the measurement and positioning for the circular workpiece was studied, so as to ensure the accuracy of the set. The computer simulation software was used to analyze and determine the distribution position of the effective measurement points inside the circular workpiece, the geometric model was established and the measurement method was selected. The simulation results and the geometric model were verified through experiments. The coordinate of workpiece center was calculated by using digital measuring probe and numerica control system. Compared with the theoretical center coordinate, the measurement center coordinate error is less than 0.2 mm, which satisfies the measurement position positioning standard and the set requirements, and the built model has better stability. The research on circular workpiece intelligent centering positioning provides a reference for the workpiece positioning under special environments.