Abstract-The nonlinear effects four wave mixing (FWM) mechanism and characteristics of semiconductor optical amplifier (SOA) were analyzed. Based on this, we proposed a method to implement optical logic AND gate based on FWM of SOA. It was approved that this method is feasible by simulation experiment. The biggest advantage of this method is that it can process higher optical signal due to the FWM effect without being limited by the carrier recovery time in SOA.