The wireless sensor network has become an important application of the customized network model, to monitor the physical environment. These sensing element networks contain limitations on system resources like battery power, association varies, and process capability. Low process power and wireless property create these networks prone to different kinds of network attacks. One is a flood attack, where exhibitions, which are not legal nodes in the network, can flow at the request of a legitimate node and break the WSN security. A flood attack occurs on the network. Suddenly, the overall performance of wireless sensor networks decreases. In this paper, a flood attack is analyzed on a wireless sensor network. WSN performance is examined under flood attack in various network parameters in depth.