Abstract: Experiments have been performed to investigate the differences between the propane/air turbulent diffusion reactive flow past blunt-body and the cold airflow under the same condition.By (Particle Image Velocimetry) PIV technique,the reactive flow fields and the cold flow fields were measured for 4 different operating modes.The velocity fields have been acquired successfully.The results show that although in general the velocity distributions of reactive flow are similar to that of cold flow,compared to the cold flow,it was found that the center of the reverse-flow zone is higher;the dimension of the reverse-flow zone is bigger;the maximum reverse flow velocity decreases and the flow fields become more turbulent.It is suggested that it is unacceptable to use cold flow experiment to simulate the reactive flow field when turbulent diffusion flame is researched in-depth.