In order to study the change of system performance of PSNRZ and DQPSK modulations when transmitting together with OOK modulation,the performance of systems that mixing 10 Gb/s OOK-RZ code respectively with 40 Gb/s PSNRZ code and DQPSK-RZ code is simulated based on the analysis of influence factors of XPM among different channels.The result shows:compared with the case that the two codes transmit independently,the performance of the mixing system deteriorates obviously,especially the DQPSK system.In this case,the transmission distance decreases by more than 500 km.