Oil drill bit composite sheet (PDC) uses diamond micropowder as raw material, cobalt metal or nonmetal element as binder, and is assembled with WC cemented carbide matrix after being mixed and sintered by high temperature and high pressure . Due to its high hardness, good abrasion resistance, and excellent impact toughness, diamond composite sheets are widely used in petroleum exploration, non-ferrous metal cutting, ceramic material cutting, etc. At the same time, the oil drill bit composite sheet is also the basic cutting unit of the PDC bit. The pros and cons of its performance have a decisive influence on the drilling effect of the drill. For the detection of PDC performance, there is no uniform standard at home and abroad. At present, wear resistance, heat resistance and impact resistance are considered to be the main indicators for measuring the quality of PDC. However, these methods are destructive tests for oil drill bits. It is understood that the ultrasonic non-destructive testing method is used to detect the internal quality of PDC in foreign countries , and there is currently no nondestructive testing technology in this area. This article through the scanning electron microscope, optical image analyzer and other analytical instruments to observe the microstructure of diamond composites, the composition of the distribution, and the diamond layer and alloy layer interface. Attempts to determine the performance of the coarse-grained diamond composite sheet without destroying the oil drill bit composite sheet.