In oil drilling the failures of PDC drill bits are exhibited as erosive wear, dropping and breaking of cutters, so 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 and their impregnated diamond composites 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 synergy is obtained. In the three kinds of WC-base matrix materials studied and their impregnated diamond composites. Their volume loss by corrosion and synergy will increase with the increase of Cu-Sn alloy contents; the increase of Ni and WC contents will lower the volume loss of matrix materials. Besides these, the resistance of erosion and corrosion of impregnated diamond composites is closely related to the bonding strength between matrix and diamonds.