We propose a Dynamic Load-balanced Path Optimization (DLPO) algorithm which can suit for different SDN-based data center network topologies. The proposed DLPO changes paths of flows during flow transmissions, achieves load balancing among different links, and efficiently resolves the network congestion problem in SDN-based data center networks. We also propose a priority-based flow table updating strategy to ensure that flows of a congested path will be redirected to a light-loaded path as soon as all flow tables of the associated switches in the light-loaded path have been updated successfully so as to avoid packet loss caused by changing paths of flows. The proposed DLPO is composed of two algorithms, which are multi-link DLPO algorithm and single-link DLPO algorithm. The multi-link DLPO algorithm can balance link loads in a network quickly to resolve some congested paths and the single-link DLPO algorithm can reroute flows to avoid using links with large loads to resolve congested paths that the multi-link DLPO algorithm cannot handle. Simulation results show that, compared to LABERIO, the proposed DLPO increases 18.9% and 9.5% of throughput per flow and bandwidth utilization, respectively, in the fat-tree topology, and 24.8% and 8.3% in the fully populated topology, both under a hot-spot traffic pattern.