In this article, a new design method of nonuniform filter banks with rational sampling factors is presented. In the method, supremum of absolute error between input and output is used as an error criteria. By minimizing this error criteria, the method gives the synthesis bank for a given analysis bank. By use of this method, strict filter specifications in other existing methods are no longer required. Furthermore, an iterative design method is extended, so that the whole filter bank system has better performance in the defined error criteria.