Plasma blasting technology is a new type of blasting technology. The design of blasting holes plays a decisive role in the overall blasting effect and blasting efficiency. In this paper, the finite element model is established for the blasting hole based on ANSYS/LS-DYNA. The numerical simulation of the wall pressure and the fracture zone of the undercut holes under blasting loads is carried out. The results show that the distortion energy changes during blasting from beginning to end. It is basically elliptical; and the smaller the aperture, the larger the accumulated energy, and the greater the damage to the rock mass; the shorter the hole depth, the smaller the energy accumulation space, and the greater the damage caused by the blasting to the rock mass; The hole depth has less impact on the lower rock mass and has greater impact on the middle rock mass. In addition, since the explosion experiment is mostly a destructive one, it is difficult to carry out the prototype test. Therefore, it is feasible to use the numerical simulation method to study the structure of the blasthole, which can be used as a reference for field work.