Abstract: In order to improve the output extinction ratio of all-optical XOR gates based on SOA-MZI structure, and optimize the performance of system, the SOA was combined with the HNLF, and the all-optical XOR simulation experiment model based on SOA-MZI was built on the simulation platform of optical communication system designing software OptiSystem7.0, and the all-optical XOR simulation experiment was carried out to two RZ format data signals at 40 Gbit/s. In addition, the all-optical XOR out signals based on SOA-MZI was optimized by a kind of optimization structure which was designed by using the nonlinear effects of HNLF, and the signal waveform diagram of time domain and eye diagram of system before and after optimizing were analyzed and compared. Through a lot of repeated experiments, the optimal system parameters were obtained to make the extinction ratio of all-optical XOR gate based on SOA-MZI be improved from 10 dB to about 28 dB. The experiment results show that the output extinction ratio of conventional all-optical XOR gate based on SOA-MZI is lower because of the incomplete destructive interference, but this problem is solved perfectly by optimizing, the output extinction ratio is improved, and the system performance is optimized.