Abstract: To address the problem that Bézier curves can not accurately represent circular arcs,a new approximation method for circular arcs by quartic Bézier curves is presented.Firstly,based on the symmetry of circular arcs and Bézier curves,the control points with unknown parameters are determined.Then according to the distribution of roots of the error function,the parameters of control points are further determined.The analytic expression of error function and the approximation order are given in this paper.Compared to the previously known best results,the approximation order of the proposed method is also eight,but the coefficient is less than half of the previously best results and thus our method has better approximation accuracy.