To effectively reduce the packet loss probability (PLP) and guarantee quality of service (QoS) of different priority bursts, a deflection routing mechanism is proposed based on priority and burst segmentation in optical burst switching networks. In the core node, contention is resolved through incorporating prioritized burst segmentation with deflection routing scheme. The burst segmentation scheme allows the head of contending bursts or the tail of original bursts to be segmented. The segmented burst is scheduled on the optimum deflection path by the parameter-tunable deflection routing scheme. An analytical model is proposed to evaluate the contention resolution scheme through calculating PLP and the normalized end-to-end delay. Results show that high-priority bursts have significantly lower PLP and the delay than low-priority. So the deflection routing mechanism based on priority and burst segmentation can effectively resolve the issue of the burst contention, and improve the performance of OBS networks.