Few existing physical layer authentication (PLA) schemes for vehicular communication network (VCN) focus on dealing with sybil attacks in multi-user mixed-velocity (mixed high and low velocity) scenario, which poses potential threats to VCN security. To tackle this problem, this paper proposes a hybrid dual-strategy PLA scheme based on channel state information (CSI) and doppler frequency shift (DS) attributes. To detect sybil tracking attacks at mixed velocities, the first step goes for grouping users into velocity intervals and tracking the CSI&DS. CSI-hypothesis testing (HT) is applied initially on the received authentication requests to classify such users. Then, a second DS-HT on either the interval containing misclassified legal (Strategy I) or illegal users (Strategy II) to improve the initial HT’s classification results. Since the authentication performance of the dual strategies is velocity-dependent, by selecting appropriate strategy for users in different velocity intervals, security analysis and extensive numerical simulations with false alarming rate (FAR), miss detection rate (MDR), and authentication rate (AR) demonstrate that the proposed scheme achieves high authentication accuracy under almost all the velocity distribution scenarios of VCN.