Good coating-substrate adhesion is an essential requirement for almost all kinds of coated devices to perform normally and stay usable for a long period. Researchers have been developing many reliable means to characterize coating adhesion and have been exploring factors that might affect the adhesion status. In this paper, the influence of substrate hardness on coating-substrate adhesion was investigated. Zr and ZrN were coated onto steel substrates with different hardness. Critical loads of coated samples were determined by scratch test combined with microscopic observation. It is found that, for either Zr or ZrN coatings, adhesion between coating and substrate increases linearly with the increasing of substrate hardness.