With the rapid development of vehicular ad hoc Network (VANET), it is gaining significant popularity and receiving increasing attentions from academics and industry in security and efficiency. To address security and efficiency issues, a self-authentication and deniable efficient group key agreement protocol is proposed in this paper. This scheme establishes a group between road-side unit (RSU) and vehicles by using self-authentication without certification authority, and enhances certification efficiency by using group key (GK) transmission method. At the same time, to avoid the attacker to attack the legal vehicle by RSU, we adopt deniable group key agreement method to negotiation session key (sk) and use it to transmit GK between RSU. In addition, vehicles not only broadcast messages to other vehicles, but also communicate with other members in the same group. So group communication is necessary in VANET. Finally, the security and performance analysis shown that our scheme is security, meanwhile the verification delay, transmission overheard and message delay are more efficient than other related schemes in authentication, transmission and communication.