Abstract: To investigate the influence of turbulent fluctuation on the infrared radiation (IR) characteristics of high-temperature round gas jet flow, the instantaneous and time-averaged values of temperature and species concentration of a high temperature round jet flow was calculated using the Large Eddy Simulation, and then the IR characteristics of the jet flow was calculated by two methods: one was based on mean temperature and another was on instantaneous temperature. The results show that the time-averaged values of the spectral IR intensity, the integral IR intensity and the IR brightness calculated by the second method are higher than that calculated by the first method. Both the differences between the results of the two methods and the IR fluctuation increase with the turbulent fluctuation and mixing layer thickness increasing, and the area that is affected the strongest by the turbulent fluctuations is the vicinity of the trailing of the high-temperature core zone in the jet flow. The difference between the IR brightness calculated by the two methods gradually decrease along the radial direction. For the round jet flow at Re=86 000 and the ratio of the temperature of surrounded air and the jet inlet temperature is 0.35, the integral IR intensity at the 90° detection direction calculated by the second method is higher than that calculated by the first method by 23.6%.