As a promising technology, the Internet of Vehicle (IoV) enables vehicles to be connected to the network and sends announcements to roadside units (RSUs) or other vehicles. Nevertheless, because of the open nature of IoV, trust and privacy are confronted with challenges from cyber attacks. Motivated by addressing the above-mentioned problems, a privacy-preserving announcement protocol is constructed in this article, in which an identity-based group signature is used to achieve anonymity of vehicles. In addition, a novel blockchain-based trust management system is designed to guarantee the authenticity of the transmitted messages while realizing the message synchronization. In the meanwhile, a joint proof of work and improved practical Byzantine fault tolerance consensus mechanism is adopted in our scheme to enhance the efficiency of verification. Security analysis as well as simulation results indicate that our proposal is suitable and effective for the IoV environment.