In order to solve the problems of low efficiency of centralized authentication and poor privacy protection in Internet of Vehicles (IOV), an efficient anonymous authentication scheme based on blockchain technology was proposed. According to the IOV's characteristics of openness, self-organization and fast movement, the tamper-proof and distributed features of blockchain technology were used to realize the generation and blockchain storing of temporary identities of the vehicles. Smart contract was implemented to make efficient anonymous two-way identity authentication while vehicles communicated with each other. Experimental results show that, in terms of authentication efficiency, the proposed scheme has the anonymous authentication with slower time delay growth and higher efficiency compared with traditional Public Key Infrastructure (PKI) authentication and identity authentication scheme with pseudonym authorization; in terms of safety performance, the temporary identity stored in the blockchain has characteristics of non-tampering, nondenying and traceability. In this scheme, the malicious vehicle identity and authority can be traced back and controlled respectively, and the public-key cryptography and digital signature technology ensure the confidentiality and integrity of communication data.