In order to improve the security and efficiency of quantum key distribution protocol, a protocol was proposed based on entanglement swapping. The two parties of communication establish the key by performing the Bell state measurement. No other people can get the key without being found. Different from the proposed protocol, the Bell measurement of any two Bell states can be realized to achieve the purpose of quantum key distribution. It does not need multi-particle entangled state but only EPR pair to realize the protocol. Analysis results showed that this protocol not only ensures the security of the quantum key shared information, but also uses the entanglement states of two photons without unitary operation. And the protocol is simple and efficient.