Abstract: In smart grid, key agreement is the key technology to ensure secure transmission and reliable communication between communication entities. The traditional smart grid key agreement scheme adopts one-to-one approach, that is, the neighborhood area network (NAN) gateway returns a key agreement reply message for each key agreement request of smart meters. When the number of key agreement requests is large, it will cause the communication delay of the NAN gateway due to the huge computational burden. In order to solve the bottleneck problem of NAN gateway in one-to-one key agreement, we propose a one-to-many key agreement scheme for NAN gateway. This scheme combined identity-based Boneh-Franklin encryption and digital signature scheme to realize key agreement between smart meters and NAN gateway. The analysis results show that the scheme can meet the security requirements of smart grid and resist a variety of security attacks. At the same time, it realizes the anonymity of smart meters. The key agreement stage has high computational efficiency and low communication overhead, which is suitable for resource-constrained smart grid scenarios.