Abstract: A data processing method of ellipse profile is presented based on the mathematical equation of ellipse.The outer envelope and inter envelope is applied to construct the model of the ellipse profile error for evaluating the minimum circumscribed ellipse and maximum inscribed ellipse under the maximum material condition.The principle for the iteration of data and the condition of termination are proposed based on mathematical equation.The validated result shows that the proposed method offers an effective way to identify the critical data points and provides an efficient approach to solve the problem of evaluation of ellipse profile.