In this paper, we propose a new routing strategy to improve the transportation performance on scale-free networks, named optimal routing strategy. It can proportionally distribute the traffic load between central nodes and the noncentral nodes. Analytical results indicate that by using the optimal routing strategy, the network capability in processing traffic is proportional to the square of the network size and is independent of each node degree. Simulations show that compared with the classic shortest path routing strategy, the new strategy can enhance the network capability several times with the small-world character and its performance is gradually improved with the increasing of the average degree. Moreover, the comparison with the efficient routing strategy also reveals the prominent performance of the new strategy.