Using dominating set can aggregate the complex physical network topologies into simple virtual topologies and reduce the cost of the networks. In the Multi-Protocol Label Switching (MPLS) network, the dominating set constructed based on label router can effectively aggregate MPLS network topology and reduce the amount of Label Switching Path (LSP), so as to save the expenses of network maintain information. However, simply considering the size of dominating set can't guarantee the best performance of the networks after aggregating. Therefore, an improved algorithm based on breadth-first search spanning tree is proposed, considering the size of the dominating set, bandwidth performance of the nodes and path length between nodes, which can effectively extend the MPLS network, with excellent bandwidth performance and reduce the data transmission delay.