Quality of Service (QoS) routing is intent to find feasible routes according to QoS constraints and optimize utilization of whole network resources. In order to solve bandwidth-guaranteed QoS routing problem, a simple but effective routing algorithm based on precomputation scheme with load balancing consideration, is proposed. The algorithm is implemented and simulated using Network Simulator (NS2). Research results showed that the proposal can keep some links free from becoming bottlenecks earlier, avoid congestion caused by unbalanced traffic load distribution, and improve performance of IP backbone networks.