The advantages of low latency, high reliability and high bandwidth of dense cellular network support real-time sensing, decision making and regulation of vehicular network. Network densification demands smaller coverage areas for base stations that are strategically deployed near consumers to support multiple services. This results in more frequently triggered handover processes. To reduce the latency induced by the handover process and ensure service continuity, this paper proposes a seamless vehicle group handover authentication protocol named SVGHP. The proposed protocol utilizes lightweight algorithms such as quadratic residual and symmetric encryption, and generates and distributes keys for group members based on the Chinese Residual Theorem to achieve handover authentication. Secondly, SVGHP includes a re-authentication phase, specifically, the vehicle group and the subsequent base stations receive the updated keys distributed by the previous RSUs for simplified authentication. And the involvement of the cloud server is avoided, eliminating the network communication delay to the core network. Detailed performance evaluation and comparison with existing protocols demonstrates that the proposed protocol is efficient in terms of computational cost and communication overhead. And in general, our scheme reduces the handover delay by at least 67.91% over the previous authentication schemes. We also provide formal and informal security proofs to prove that our protocol meets common security requirements.