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.