Abstract: In order to overcome the limitations in power, computation, storage space and band width, a key management scheme for clustered wireless sensor networks was presented. Combinatorial design is adopted in this scheme so that the nodes in the same cluster can directly establish shared keys while the ones in different clusters can set up a multi-path key through the base station. The theoretical and simulation results show that with the key management scheme, the probability of network connectivity is 1 when the number of node's keys is more than 10.