As the main computing paradigm for resourceintensive scientific applications, Grid[1] enables resource sharing and dynamic allocation of computational resources. It promotes access to distributed data, operational flexibility and collaboration, and allows service providers to be distributed both conceptually and physically to meeting different requirements. Largescale grids are normally composed of huge numbers of components from different sites, which increases the requirements of workflows and quality of service (QoS) upon these workflows as many of these components have real-time requirements.In this paper, we describe our web services based QoS-aware workflow management system(WfMS) from GridCC project[7] and show how this WfMS can aid to ensure workflows meet the pre-defined QoS requirements and optimise them accordingly.