Abstract: Based on the change of rock macroscopic crack, fracture problem caused by rock crack during the drilling with impregnated diamond bit was studied. A simplified rock fracture equivalent model was established with simplified stress and crack by using the rock fracture mechanics theory combining practical working conditions in the process of drilling, a new rock fragmentation mechanism of impregnated diamond bit with grids matrix was analyzed theoretically. The results indicated that special grid structure can effectively increase drilling pressure to press into rock to induce crushing cavity and crack compared with that of the conventional impregnated diamond bit, pressure per unit area increased by 67%, from 68.03 kgf/cm² to 113.33 kgf/cm². Special grid structure is conducive for the flushing fluid to store, better to improve the cooling effect of diamond particles, and to break rock matrix in a more beneficial way of tensile crack.