Optical burst switching (OBS) is one of the most important switching technologies in the future optical WDM networks and Internet. The differentiated services model and architecture are proposed for optical burst-switched WDM networks. A new data burst scheduling scheme "differentiated scheduling" (DS) is designed to support OBS differentiated services. By dynamically choosing the early differentiation time, each OBS node can adjust the data burst loss rates for different classes of bursts and satisfy differentiated QoS requirement with the available resources.