In this study, the effects of the vertical load on the scraping test are evaluated for TiN/T8 and NiP/WC-Co coating-substrate systems. The study shows that there exists a range of tile critical vertical load for the successful scraping test. A mechanical analysis for the force and deformation nearby the tip of the scraping blade shows that the vertical load is indispensable for equilibrating the reactive force to thrust the blade up from the substrate surface and for compensating the wear of the scraping blade when the blade wedges into the interface between the coating and the substrate. The results of the study have also revealed the principle for the determination of vertical load, the requirements fur the materials properties of coating-substrate system and the extension in which the scraping method is applicable.