[Objective]Aiming at the security risks of the authentication key negotiation scheme in the existing vehicular ad-hoc networks (VANETs) under the threat of quantum computing, a novel authentication key negotiation scheme integrating classical cryptography and continuous variable quantum cryptography is proposed. [Methods]The scheme utilizes the quantum teleportation property of continuous variable quantum graph state (CVGS) to realize the authentication between vehicles and roadside units, and combines with secure hash function to complete the key negotiation. [Results]The security analysis shows that the scheme can effectively resist quantum computing attacks in a short period of time and satisfy the security requirements of authentication and key negotiation. Performance evaluation shows that compared with the existing quantum cryptography scheme, the number of required quantum states is reduced by half, which improves the feasibility of realization; compared with the traditional classical scheme, the computation and communication overheads are reduced by 77.27%和63.76%, respectively. [Conclusion]This scheme achieves a good balance between security and performance, and has a wide range of application prospects and practical deployment value, which can provide effective security for VANETs in the face of quantum threats.