Abstract. This paper researches the theory of geometric error evaluation and its application. On the basis of the geometric model of error evaluation, the features of the geometric error enclosure evaluation are analyzed, and the paper has founded the linear programming model of minimum zone association, maximum inscribed association and minimum circumscribed association. By taking the minimum conditions criterion and the theory on minimizing the extremal difference function as rules of geometric error evaluation, a correctional simplex method for direct solution of the programming model is proposed, and also the process is given. Furthermore, the method is verified by giving an example of the cylindricity error evaluation and comparing the experiment results with the ones obtained from other common methods. In addition, this designed method is also used to other geometric error evaluation in practice. The theoretical analysis and experimental results indicate that, the proposed correctional simplex method does provide well accuracy on geometric error evaluation. The outstanding advantages conclude not only high efficiency and stability but also good universality and practicality.