In wireless sensor networks (WSNs) handling mobility of nodes in key management is a challenging task. In this paper, a mobility management technique for keying scheme of WSNs is presented. The technique selects nodes with high energy resources, wide communication range and high processing capacity as cluster heads. Cluster keys for cluster heads and pairwise keys for nodes are generated by the sink through exclusion basis systems. Whenever a node moves from currently connected cluster to another in the network, the mobility based key management scheme is triggered. The sink verifies the authenticity of roaming node and allocates it to a nearby cluster. New pairwise keys are generated and transmitted to the roaming node through newly connected cluster head. Further, a key organization technique is presented to ensure the forward and backward secrecy of nodes. The proposed technique is simulated in NS2 and simulation results show the efficiency of our technique.