Abstract: Taking multi-constraint into account, such as cost, power and network performance, the wavelength may be assigned to fit further the actual network configurations. However, the problem of wavelength assignment will be more complex correspondingly with a hierarchical solution needed. As the sub-problem at each level is NP complete, the genetic and heuristic algorithms shall be used jointly. A simulation software was thus designed and implemented, by which the results show that the proposed algorithm can solve well the multi-constraint wavelength assignment in IP/DWDM optical Internet, i.e., not only obtaining the optimal configuration under the conditions as above, but also meeting the user connection requests as possible.