This paper aims at the problems of low drilling efficiency， low core recovery， large disturbance and high accident rate during the coring process of deep-sea hard rock， discusses the fracture mechanism of deep-sea hard rock under the combined conditions of rotary and impact taking the deep-sea hard rock as the research object and using the finite element numerical analysis software. The results show that the rotary rock breaking method can effectively improve the drilling efficiency. In the drilling process，15~25kN WOB and 4~6 mm boss height can be optimized. Under this condition， the ROP is faster， the core quality is higher， and the energy utilization rate is also higher. The closer the working frequency is to the optimal frequency ，the more efficient the drilling will be as long as the strength of the jarring component allows.