To overcome the shortages in security and privacy of existing handover authentication protocols for vehicle network, an improved scheme based on the Lightweight Identity Authentication Protocol (LIAP) protocol is proposed in this paper. Firstly, terminal’s pseudo-identity is concatenated with a random number, then quadratic residues operation is utilized to encrypt the connected information and to generate a dynamic identity, which can protect the user’s location privacy. Meanwhile, the new road side unit regenerates a new session secret sequence and computes the challenge sequence with the terminal user’s pseudo-identity by XOR encryption, which can provide secure protection against parallel session attack during the handover process. Theoretical analysis and experiments show that the proposed protocol can not only meet security requirements of providing terminal anonymity and defending various attacks, but also achieve a faster switching speed. Therefore, the improved protocol shows obvious superiorities over most existing schemes.