Multi-cluster Grids have emerged as the most popular type of grid environments. On multi-cluster grid, resources are distributed across different networks. Hence, scheduling and dispatching jobs are difficult and inefficient due to the restrictions of network and the communication overhead. This paper presents the design and implementation of an efficient GridRPC system for the multi-cluster grid. Metascheduling mechanism is developed to distribute jobs onto different clusters of computers effectively. Further, a dynamic bundling mechanism is provided to reduce overhead of job dispatching. This mechanism bundles similar requests to form a composite request that is dispatched to a grid resource. The above mechanisms have been tested with different types of services and loads, and the results show that they help to achieve more balanced workload and reduce the overhead of job dispatching. This cuts down execution time of applications.