The const rained complex method is one of the important w ays to resolve the problem of nonlinear optimizat ion. The iterative calculating method of const rained complex method in concave feasible fields is discussed in this paper. In view of the situat ion that the central po int of complex is out of the feasible f ields, the common complex algorithm is modified and a new method of iterative calculat ion is provided for engineering calculat ion. At the same time, through the contrasting calculation of an engineering opt imizat ion problem, the astringency and engineering usability of this modifier algorithm are proved. The computat ion results show that the method of modif ier algorithm of const rained complex method in concave feasible fields, proposed in this paper, is ef fective.