This paper presents a new key management protocol of wireless sensor network based on NTRU public key cryptosystem, which includes node authentication using the NTUR digital signature and showing an implementation process of establishing encryption key between nodes, adding a new node, and eliminating the invalid nodes. This paper also analyzes the security of the protocol, the storage overhead, communication overhead, and calculation speed. The analysis showed that our protocol has the advantage of good security, simplification of design, small amount of calculation, and less resource consumption so that it is suitable for wireless sensor networks.