Abstract: A secure key distribution protocol for WSN is put forward based on cluster—SEKD，which can afford deterministic security and reduce networks energy consumption and the storage cost compared with existing typical secure protocols.SEKD agreement can efficiently and dynamically set up cluster key for each clusters，and distribute cluster key by cluster head one-time local broadcasting based on the difficulty of factorization of polynomial，and maximize saving communication and encryption-decryption cost.Because of multi-hop routing，SEKD uses multiple encryption to guarantee the security of the data.Performance analysis and simulation results show that，under the premise of meeting the security requirements，SEKD can efficiently set up cluster and inter-cluster key for WSN，significantly lower network energy consumption，and extend the network survival time.