In order to improve the efficiency of the directional cracking of hard rocks,starting from the mechanism of cracking from hard rocks to breaking rocks,based on the empty hole effect theory,the stress variation law of the empty hole wall under the 200 mm、250 mm、300 mm、400 mm hole spacing and the 20 mm、40 mm、90 mm、120 mm hole radius is studied,and the theoretical calculation and numerical simulation are compared and analyzed to verify.The results show that the existence of empty hole makes the stress concentration near the expansion hole,with the increase of empty hole spacing and the decrease of empty hole radius,the stress concentration of empty hole effect becomes weaker.The maximum tensile stress appears on the connection line of the empty hole and the expansion hole.The maximum pressure stress appears near the empty hole circle 70°.The stress intensity factor of type I rock on the inter-hole connection line corresponds to the law of stress variation.When the hole spacing reaches 400 mm,the stress intensity factor KI is smaller than the fracture toughness KIC of rock and the condition for formation of through cracks cannot be reached.According to the research results,set the parameters of the empty hole and in Shenzhen Tiegang-Shiyan reservoir Shiyan North clear water diversion tunnel to carry out the rock breaking test.The test results show that empty holes play a guiding role in the direction of crack propagation,which can cause the main crack to form on the connecting line between the empty hole and the expansion hole and is beneficial to improving the efficiency of the breaking rocks in hard rocks,which can provide reference for similar projects.