Abstract: The use of propagation law of wave and mechanical knowledge, propagation form of stress wave in the vicinity of the free surface was analyzed, and the rock stress relationship expressed by reflection coefficient before and after free surface reflection was obtained, and the reflected stress decreases with the increase of stress wave incidence angle on free surface. According to the column blasting rock failure characteristics, the rock containing the free surface is divided into blasting cavity, fracture zones, elastic and reflective stress tensile failure zone, and coal pre-splitting blasting method for protecting the integrity of free surface is proposed. LS-DYNA program is used to simulate blasting stress wave propagation in the form of the free surface and the non-reflective side of the interface, the result is that the stress wave reflected at the free surface and formed stress wave reflection area in the range of 0.5 to 0.8 m away from the free surface.