In view of problems of low breaking efficiency and serious wear of hammer head when using drilling + rock drilling (DRD) rock breaking process to deal with extremely solid rock on the seabed of a certain anchorage,simulation and engineering tests on the effect of rock breaking on extremely solid rock under different drilling spacing are carried out.The development process of internal stress damage and the breaking effect under different pore placement parameters are analyzed.The results show that when DRD removes extremely solid rock from the seabed,the best rock breaking effect is achieved by using a 35 t axe type rock drill hammer to break the rock mass at a 0.4 m×0.5 m（width×length）drilling spacing.Influenced by the shape of the hammer head and the airspace,the internal stress of the rock mass spreads to the two sides of the parallel hammer head,the side of the airspace,and the deep part,forming a damage area dominated by tensile and tension-shear damages.Compared with the square hole placement scheme,the rectangular hole placement scheme significantly enlarges the damage range and has better rock-breaking effect.