Abstract: In order to improve the security and efficiency of secure communication in quantum key distribution (QKD) networks, this paper proposes a multipath key transmission method. Firstly, the link cost function is calculated according to the contribution rate of the node to the link and the freshness of the key. Secondly, the multipath selection algorithm based on minimum heap optimization is used to select the optimal paths. Finally, the key block transmission is applied to realize the simultaneous transmission of the key on multiple optimal paths. The experimental results show that the proposed multipath key transmission method is more secure and efficient.