Abstract: The circular interpolation is widely used in NC manufacturing of curve contours. Because the Min-error interpolation method for the circular interpolation is complicate and low efficiency, the problem of precision and efficiency about circular interpolation algorithm are discussed in this paper. A revised interpolation algorithm based on Min-error interpolation method is proposed, and the problem of unified programming in four quadrants is discussed. The revised interpolation algorithm has the advantages of simplicity, good path precision and short running time.