Effective and efficient Quality of Service (QoS) management is critical for a service grid to meet the requirements of both grid users and service providers. We incorporate QoS management into Open Grid Services Architecture (OGSA) and provide a high-level middleware to build complex applications with QoS guarantees. We introduce a scalable framework of information service in which capabilities of services are described and advertised as metadata of grid services. Based on that, a QoS policy based dynamic service scheduling strategy is proposed. The experiment result on the prototype proves the availability of our framework.