In migrating workflow system, the security and route of migrating instance for the completion of the workflow plays a vital role. This paper presents a migration strategy based on immune algorithm. This method draws on the immune system's features, encodes migrating instance’s needs and security requirements as antigen and work location of service information and security as antibody, and simulates the matching process of the immune system in order to get the migration routes dynamically. The algorithm considers both the resource requirements of Agent’s task and the security of the workstation according to Agent’s risk in order to achieve safer route planning. The simulation results show that the algorithm effectively avoids the malicious host, significantly reduces the probability of migrating instance attacked and enhance the security of migrating instance.