A novel differentiated service hybrid (DSH) signaling protocol is proposed for optical burst switching (OBS) networks. In an OBS network, real-time (circuit) traffic and non-real-time (bursty data) traffic are dealt respectively by TAW and JET protocol according to their different QoS requirements. TAW signaling is modified to adapt to the transport of circuit emulation traffic. A call request of circuit traffic may be used to set up a virtual channel from a source to a destination before the traffic arrives, and the virtual channel would be held until the call ends. In this way, smaller end-to-end delay and lower loss probability of data bursts may be achieved for accepted calls. By computer simulations, the performance of DSH protocol is studied; its effects on wavelength utilization and blocking probability of OBS network are investigated.