SDN is a novel network architecture that separates the control plane from the data plane. It usually utilizes a centralized controller to manage all the switches in the network. With the expanding of network scale, both the complexity of computing routes and the amount of messages exchanged between controller and switches are increasing sharply. The limited performance of a single controller will cause congestion in the control plane. Some schemes have been proposed to solve this problem by dividing the network into multiple domains. In this paper, we propose a cross-domain source routing scheme for multi-domain network combining the thinking of source routing with pre-routing. The cross-domain flow set-up requests are generated only in the source domain and the destination domain. Each controller just needs to bear the load that related to the local traffic. The simulation results show that the scheme can reduce the load of controllers comparing with other schemes.