The influences of the injection current and carrier lifetime of semiconductor optical amplifier(SOA) on the switching window of ultrafast nonlinear interferometer(UNI) were studied by proceeding simulation and experiment.The gain of SOA is directly proportional to the injection current and is inversely proportional to the carrier lifetime.The increase of the injection current can increase the gain of SOA and the height of switching window of UNI.The decrease of the carrier lifetime of SOA increases the speed of carrier recovery and is beneficial to the switching window.In our experiment of 10 Gb/s UNI,continuous light is used to replace the signal pulses in order to observe the switching window.When changing the injection current of SOA,the variations of switching window of UNI influenced by it could be verified.The result of experiment shows that the more value of injection current of SOA is good for the switching window of UNI on the condition that the shape of switching window of UNI is unchangeable.It could make the height of switching window increase.This result is same as the simulation.