WLANs have evolved into the best choice in a number of situations such as government institutions and airports, but because of the open transport in these networks increased the possibility of security attacks, which required the use of security protocols to protect the network and to protect users. This research examines and evaluates the impact of security protocols on WLAN performance in order to select the optimal protocol, the impact of these protocols on network performance has been evaluated by adding those Protocols to open source GloMoSim environment, And recent simulation results show that the performance of these protocols are varies according to the environment applied within them, noting that there is no effective Protocol in all environments, i.e. the suitable Protocol in an environment may be unsuitable in other ones. After comparing performance results in simulations with performance results in the real network, we can see that the best performance protocol is WEP. Also, The best protocol for both performance and security is the WPA2. Hence, our choice to one of the security protocols depends on what we want to secure in the level of protection and the performance of the network.