Abstract: A weighted PIA algorithm for implicit B-spline curve fitting data points is proposed. Firstly, the offset point set is generated by using the data points to be fitted and the given normal vector. Then, the difference vector is constructed by the offset point set, so as to obtain the error control coefficient to be adjusted. In order to make the iteration efficiency higher, the error control coefficient is weighted in the iteration process. Finally, the curve of the fitted data points is obtained by using the latest control coefficient matrix.