Abstract: Most of the existing polynomial approximation methods of circular arcs do not preserve the arc lengths.To solve this problem,a new polynomial approximation method of circular arcs is proposed,where the result curves have the same endpoint positions,tangent vectors,and lengths as the given arcs.Here the PH curves are involved since their arc lengths can be represented using polynomial form.The accurate representations of the results in quintic PH curves are provided.Numerical examples are given to show the effectiveness of the new method.