Abstract: A non-NP QoS (quality of service) multicast routing algorithm in IP/DWDM optical Internet, which is one of the main networking technique of NGI (next generation Internet) backbone, is proposed to construct an optimized QoS multicast routing tree based on THGA (tabu-hierarchy genetic algorithm). The algorithm imitates the biologic propagation process and adopts the hierarchical coding scheme with two tabu operators (tabu crossover and tabu mutation) introduced to improve the genetic operation, taking account of user's requirements for QoS and network cost to benefit the balance in network load. Simulation results showed that the proposed algorithm is both feasible and effective in overcoming the specific shortcomings in the QoS multicast routing algorithm just based on the classical GA to a certain extent, such as prematurity and slow convergence. It not only improves the efficiency and performance of algorithm but provides a better way to construct the QoS multicast routing tree in IP/DWDM optical Internet.