Abstract: Tunable Diode Laser Absorption Tomography(TDLAT) technique is a new technique for 2D flow field diagnostics, which combines the Tunable Diode Laser Absorption Spectroscopy technique (TDLAS) and the computer tomography (CT). It has wide applications in hot, high-speed and toxic gas diagnostics, especially for combustion and propulsions in harsh environments, due to the merits of high sensitivity and noise resistance. Firstly, the fundamentals of the TDLAT are presented. Secondly, the TDLAT system is divided into four stages:the optical measurement system, the data processing system, the reconstruction algorithm and the data presentation. The progressing on the four stages and key technologies are discussed. Thirdly, some examples of applications of TDLAT sensors in practical combustion diagnostics are presented, including scramjet engines, aero-propulsion engine and coal-field combustion. Finally, the development tendency and conclusions are given. This paper can provide reference for the researchers to comprehend the progress and key techniques of TDLAT.