Abstract: The problem of acoustic radiation restricts the performance of aero-engine. To further reveal the acoustic radiation mechanism of mixing layer under supersonic flow, and enhance the understanding, this paper studies the acoustic characteristics of supersonic mixing layer. The near field calculation is investigated by numerical simulation of parabolized stability equations (PSE), and an integral theory based on stability theory is applied to predict the far field acoustic pressure. The intensity and direction of Mach wave are calculated and in good agreement with previous results. The influence of the flow temperature at the upper and the lower sides is discussed in detail. The results show that, the slow mode dominates when the temperature ratio is less than 1, while the fast mode dominates when the temperature ratio is greater than 1.