IP/DWDM optical Internet is considered to be one of the most potential candidates for NGI (Next Generation Internet) backbone. However, the bottlenecks caused by the electronics still exist. A solution to this problem is to design an optimal virtual topology. In this paper, a novel virtual topology design method is presented, minimizing the sum of traffic-weighted hop count. Based on the given physical topology and the specific traffic matrix, the corresponding virtual topology is designed, and then, over which the traffic is routed. Due to its NP-hard nature, the design problem is decomposed into three subproblems: virtual topology construction, wavelength assignment and traffic routing, which are solved with heuristic algorithms respectively. To verify the feasibility and the effectiveness of the proposed method, a simulation environment is developed and simulation has been done over some actual network topologies. Simulation results have shown that the proposed method is both feasible and effective.