The variation rules of granite dynamic tensile mechanical properties are summed up, which are under the conditions of being cooled under different high temperatures, different loading rates and random fracture development; according to the process of down-hole rock cracking by roller bits, analysis is made on the curve of loading-fracturing depth under the coupling dynamic and static loads, the loading point of coupling dynamic and static loads should be at unloading stage of static load. Fracturing depth and volume of rock mass under dynamic and static loads are discussed based on the different pressure values, it is indicated that the efficient rock fragmentation and crack development could be carried out through enhancing static load and impact force, preloading static pressure to make pre-stress damage on rock and loading unloading loading fracturing circular mode. By the rock-socket pile foundation engineering practice, it is showed that by optimizing the structure and teeth arrangement, applying dynamic and static loading mode and cooling treatment of bit, the roller bit can realize high efficiency drilling in slightly weathered granite, which provides import technical support for the application of roller bit in rotary drilling bored piles construction.