Since many of the key techniques now being applied in building services and a lot of service-based applications were developed, Service-Oriented Computing (SOC) has become the main trend of distributed computing research field. In this paper, we proposes a workflow-based middleware named ShanghaiGrid Support Platform (SGSP) for SOC in the Grid environment, which provides a grid toolkit for ShanghaiGrid application developers and specific grid constructors. The toolkit can access, invoke and compose diverse services conveniently. The architecture and function of the each component of toolkit have been introduced in the paper. We also use an image processing application to validate the feasibility and efficiency of SGSP.