Multi-service SDH networks support both packet- and circuit-switched traffic. Optimal design of such a network means to guarantee the circuit connections and configure a logical packet-switched topology with lowest congestion. This letter first formulates the problem as a mixed integer linear programming, which achieves optimal solution but has high computation. Then a heuristic algorithm is proposed to yield near-optimal solution efficiently. Performance of the algorithm is verified by an example. Multi-service SDH networks support both packet-and circuit-switched traffic. Optimal design of such a network means to guarantee the circuit connections and configure a logical packet-switched topology with highest congestion. This letter first formulates the problem as a mixed integer linear programming, which achie achieves optimal solution but has high computation. Then a heuristic algorithm is proposed to yield near-optimal solution efficiently. Performance of the algorithm is verified by an example.