Aiming at the system performance degradation problems of distributed file system in massive small file access patterns, designed and implemented a delegation mechanism for meta data cache in client .The client apply some kinds of delegations when getting meta data from the server. The meta data server checked and decided ecide whether to grant the delegation or not. Once the client getting the delegation which is stored in the local memory, the meta data getting operation can be unnecessary to sent RPC request. The simulation result shows that our method in this paper can reduce the number of the RPC request effectively, and aving valuable network bandwidth resources, reducing the metadata server load.