Abstract: Due to the close acoustic impedance of radar absorbing coating (RAC) and carbon fiber substrate, the ultrasonic echo signal is too weak to be recognized accurately by the ultrasonic thickness measurement software, and recognizing pulse echo acoustic path difference manually is subjective and inefficient. To solve this problem, a coating thickness measurement method based on theoretical analysis combined with Matlab batch signal processing technology was proposed. Firstly, the phase change relationship of the echo signals on the upper and lower surfaces of the coating was determined by theoretical analysis. Then, the ultrasonic pulse echo signals were read in batch by Matlab script, and the time domain range of the peak (valley) of the echo signals on the upper and lower surfaces of the coating was manually selected. The position of the peak (valley) was confirmed by the script, and the echo acoustic path difference was calculated. Finally, the thickness of the coating was calculated based on the propagation rate of the ultrasonic wave in the coating. The thicknesses of two kinds of radar absorbing coatings on carbon fiber substrate were measured by this method. The results show that this method can not only meet the requirement of thickness measurement accuracy, but effectively solve the problems of subjectivity and low efficiency when recognizing the pulse echo path difference manually, so it has a good prospect of engineering application.