Grid computing is becoming a mainstream technology for large scale distributed resource sharing and system integration. Workflow management is emerging as one of the most important grid services. In this paper, we present an agent-based grid workflow management system (AGWMS) using artificial intelligence (AI) planning technology. AGWMS has a four layer architecture. The agent layer makes the system more robust, flexible and intelligent. AI planning technology is utilized in the system. The adapter layer makes it easily that AGWMS invokes external applications.