This paper presents a contour fitting algorithm which combine Freeman chain code and error control of B-spline curves. Firstly, it uses Freeman chain code boundary tracking method, based on the difference between adjacent pixels variation of chain code, eliminate false feature point, the vast majority of the extracted contour feature points, and then combined with error control based B-spline curve method, to obtain feature points which can accurate represent contour information. This method of avoiding the use of strike curvature characteristic points for complex calculations to improve the feature point detection speed, and the extracted contour to precisely fit the local support points, error control based on the realization of the profile curve fitting. Experimental results show that the algorithm is correct.