This study discusses in detail turbulent diffusion flame structures and their similarities by using laboratory-scale turbulent diffusion flames. The characteristics of these flames vary with working conditions, burner sizes, type of fuel, oxidant, etc.. The time scale and PDF of temperature fluctuations were obtained by laser Rayleigh scattering spectroscopy (LRS) which had no direct interference with the combustion field during measurement. A He-Ne laser LDV system was also adopted to measure the velocity fluctuations. The turbulent diffusion flame structure could be classified into four regions by the time scale characteristics of temperature fluctuations. From the results of cross correlations between velocity and temperature fluctuations, it uas ascertained that the turbulent energy flux was not simply proportional to the gradient of the time mean temperature profile in the combustion region where the time scale of temperature fluctuation attained almost the maximum value