Owing to the unique properties of quantum mechanics, the quantum key agreement has unconditional security in theory. In this paper, a quantum key agreement protocol is designed. The four-particle cluster states are used as quantum sources. Two communication parties conduct joint Bell measurements respectively, and code through the controlled NOT gate and Hadamard gate to achieve shared secret. Here, weak measurement and quantum measurement reversal methods are used to deal with decoherence during transmission. The proposed key agreement protocol not only has the ability to respond to various participant and external attacks but also has higher communication efficiency.