This paper firstly applies a Sequential Number-Theoretic Algorithm for Optimization (Fang and Wang, 1990) to evaluate the form errors of machine parts. By this method, it's not necessary to completely depend on the initial value of the parameters. It can be applied to any evaluation of linear or nonlinear parameters, and it is easy to find an optimum overall in the problem in which there are more partial extreme values. This algorithm is superior to the traditional algorithms. Several numerical cases on the evaluation of form errors are given in this paper.