Abstract: The laboratory audit criteria of NADCAP coating were analyzed. Combined with the technical requirements in the process of metallographic examination, the test procedure and basic technical requirements for establishing the NADCAP laboratory of coating were introduced. The relevant content was applicable to the preparation of coating samples related to metallographic examination, microstructure evaluation, microhardness test and metallographic method to determine the thickness of the coating. At the same time, the root causes of non-conformities in the field test process were analyzed, in order to provide reference for the improvement of coating laboratory testing technology and the acquisition and maintenance of NADCAP coating laboratory qualification.