The Vehicular Adhoc Network (VANET) is a communication model that is used today that takes place between the vehicles for exchanging the messages or information about road traffic and road conditions, to make the driving comfort. In the VANET the security and decision making are the two important promising challenges and factors. This paper proposes the identification of Sybili attack and it is challenging task in VANET. The sybili attck, where the user uses the multiple identities at the same time and it broadcast the messages to other vehicle that were connected in the network. This attack is very difficult to identify in the vehicular network. In the previous work, the message verification approach is used, but the problem here it is, this approach not able to detect the attack of the Sybili in the vehicle in prior. To solve this problem, the Diffie Hellman Key algorithm is used for the Sybili attack detection. By using the secret key in the vehicles it reaches the correct destination in VANET. The simulation experimental results were shown and it identifies the Sybili attacks in Vehicular network efficiently and effectively.