With the fast advance of wireless chip-set and portable devices, mobile ad-hoc network (MANET) is becoming a novel wireless computing environment that can embrace grid computing by utilizing the nontrivial computing capabilities of each node to solve time-critical or resource-critical problems. But a few issues such as intermittent network connectivity, node?s heterogeneity and resource constraints, must be addressed carefully. For them, a mobile agent approach is proposed in this paper. It delegates computation jobs to mobile agent, drives it to migrate on MANET and find nodes that have the resources. On each node, agent negotiates to use it resources and does its best to accomplish the jobs. This approach enables flexible handling of various resource sharing policies, and considers each node?s resource capabilities. Moreover, it shields the dynamical network connectivity to mobile agent, thus enables logical mobility of grid applications over MANET.