Abstract: Vehicular Ad Hoc Networks (VANET) has attracted today’s research efforts. Despite the attention that VANET research got, current solutions to attain secure VANET still undergoing to protect the network from oppose and attacks. The necessity for a secure VANET networks is powerfully tied to the security and privacy features. This Jamming attacks are one of them. These occur by transmitting continuous radio ways to inhibit the transmission among sender and receiver. These attacks affect the network by decreasing the network performance. Previously there had been considerable research in the field of increasing the performance of network by using routing protocols. In this paper we are analysing the performance of Vehicular ad hoc networks under jamming attack. This work includes a network with high mobility, using IEEE Along g standard with improved AODV (Ad hoc On Demand Distance Vector) routing protocol parameters. Video conferencing and FTP with high data rate are being generated in the network. For the Simulation purpose we employed OPNET (Optimized Network Engineering Tool) MODELER 14.5 is used for simulation. The performance of network is measured with respect to the QoS parameters like, network load, retransmission attempts, media access delay and. Throughput.