Accurate evaluation of roundness error is of great significance for improving machining accuracy and ensuring working accuracy of parts.Aiming at the problems of low evaluation accuracy of roundness error and slow calculation speed,a roundness error evaluation algorithm,namely circular segmentation algorithm,was proposed.A new mathematical model was established.The circle segmentation algorithm was combined with the geometric judgment of the minimum containment area method to evaluate the roundness error.The least squares circle center was used as the initial circle center,and a circle was made with a certain radius.After iteration,the position of the real-time circle center was searched,and then the geometric structure of the intersecting chords was used to judge,finally the circle center of the minimum containment area was obtained.This method did not need to meet the assumption of equal interval sampling and small deviation.After algorithm verification,the roundness error was evaluated and compared.The results show that the roundness error evaluated by using this method has high accuracy,fast calculation speed and good stability.