Abstract: In oil drilling the erosion and corrosion resistance of the matrix is one of the key factors affecting the quality of PDC bits.In order to understand the degradation mechanism of matrix materials for drill bits,a kind of loop recirculation rig is adopted to measure total mass loss TML,mass loss E by pure mechanical erosion,and then through calculation the mass loss C+S by corrosion and their synergy is obtained.The tested and calculated results show that TML of matrix materials is not only caused by pure mechanical erosion,but also by corrosion and their synergy of mechanical erosion and corrosion,which tells us that the corrosion resistance of matrix materials should be considered carefully besides their erosive resistance in the design and selection of PDC drill bits used in the corrosive drilling mud.