In this paper, we propose an adaptive routing approach for video streaming with QoS (Quality of Service) support over Software Defined Networks (SDN), called ARVS. In our approach, base layer packets and enhancement layer packets of video bit streams are treated separately as two levels of QoS flows (level-1 and level-2 QoS flows). During video streaming, if the shortest path does not satisfy the delay variation constraint, the base layer packets have the first priority to be rerouted to a calculated feasible path based on the available bandwidth of this path, and the enhancement layer packets will stay on the shortest path. However, if there is no available bandwidth in this path, the base layer packets will stay on the shortest path while the enhancement layer packets will be rerouted to this path. In this way, the video quality would be enhanced due to the congestion of the shortest path has been mitigated. Simulation results have shown that, compared with OpenQoS, our approach can reduce up to 77.3% of the packet loss rate for the base layer packets of video bit streams and also enhance at least 51.4% coverage under various network loads of the shortest path and the feasible path.