A simplex method for function minimization in optimization theory is implemented to numerical solution of dispersion relation for nonlinear dielectric waveguides.Propagation characteristics of nonlinear dielectric waveguides for two examples are analyzed by using this method.One is an asymmetrical planar layered structure consisting of an optically linear substrate,a Kerr-law core,and a linear cladding (LNL-type);The other is a symmetrical planar layered structure consisting of optically nonlinear Kerr-law substrate and cladding,and a linear core (NLN-type).Numerical results demonstrate that this method is simple and efficient for analyzing characteristics of nonlinear waveguides in cases where numerical solutions of complicated dispersion equations are difficult.