Over the last two decades Free-Space Optical communication (FSO) has become more and more interesting as an adjunct or alternative to radio frequency communication. In this paper, performance of Free Space Optical (FSO) communication in the presence of atmospheric turbulence is presented. FSO system required free line of sight between the transmitter and receiver. Light travels through air faster than it does through glass. Different factors that affect the performance of the communication channel in free space optical communication system is presented with different channel model such as Rayleigh, Rice and Nakagami models. The performance controlling parameters are outage probability and Bit Error Rate (BER). Simulation results show the performance of different channel models with different level of channel turbulence in FSO system. Results also show that as the signal to noise ratio increase, BER goes on decreasing and try to approaches the theoretical value.