Abstract: Scanning acoustic microscope (SAM) is effective in acquiring the information about subsurface of samples nondestructively. Due to its pronounced nondestruction and subsurface detecting capability,SAM has been finding a wide range of application in materials science and biology. In order to enlarge the application spectrum of SAM, research of wear of materials by SAM has been conducted. A reflection type SAM with a frequency of 150 MHz was used to observe the wear process of atmospherically plasma sprayed Al 2O 3 40%ZrO 2 ceramic coatings and compare the wear mechanisms of ceramic coatings (Cr 2O 3, ZrO 2 8%Y 2O 3) and metal alloy (N + implanted Cr Mo V steel), which are typical brittle material and plastic material, respectively. These results could be helpful to understand the wear mechanisms of materials. The SAM results have been testified by SEM observation.