Abstract: In the measurement of coating thickness with UT technique, it is different to identify the reflected interface echoes in the time domain due to the interference of the UT signals from the surface and interface of the coatings. Continuous wavelet transform with Mexh Hat was applied in UT A-signal analysis, the modulus maxima was calculated and adopted as the criteria in the identification of the reflected signal from interface of the coating. The coating thickness was then determined by the UT velocity in the coatings and the time of interface reflected echo. The above measured Al coating thickness was checked with optical microscope analysis of the same coating, satisfying results were achieved.