Abstract: Drilling and blasting methods, such as in mining, tunnel construction, and hydropower, have been widely used in the field of rock excavation because of their efficiency, ubiquity, and cost-effectiveness. However, because of the immense power of explosions, excavating rock masses through blasting often results in destructive effects. For example, in a tunnel (roadway) excavation, the blasting of peripheral holes can cause serious overbreak/underbreak of the contour surface, resulting in a large excavation damage area, which affects the stability of the tunnel (roadway). In the self-formed roadway without coal pillars, if the roof-cutting line is not properly controlled, a large area of crack propagation will occur in the roadway roof, which directly affects the stability of the “short wall beam,” causing large deformation and even collapse of the roadway. Therefore, the accurate control of the direction of blasting crack propagation and the directional fracture of the rock mass have become key issues in the field. Considering that the tensile strength of a rock mass is much lower than its compressive strength, a blasting technique called directional tensile blasting (DTB) is proposed, which produces an approximately two-dimensional single crack surface in the predetermined direction of the hole wall after blasting, eliminating the damage of the reserved rock mass caused by conventional blasting. However, the mechanism of directional fracturing caused by DTB remains unclear. Therefore, this study conducted theoretical analysis and indoor experiments to explore the directional fracturing mechanism of DTB. The directional fracturing principle of DTB was analyzed, visualization experiments on the expansion of DTB cracks were conducted using a self-developed experimental system, and a directional roof-cutting test using DTB technology was conducted in an actual coal mine. The research results show that DTB generates high-temperature and high-pressure gas in the hole through the instantaneous reaction of the expander, which causes an instantaneous expansion and cracking effect on the medium while controlling the direction and number of cracks initiated and propagated through a tensile blasting device. DTB generated concentrated tensile stress on the hole wall in the presplitting direction by controlling the tensile blasting device, resulting in mode I cracks through tensile fracturing, transforming the random and partitioned rupture of conventional blasting into a directional and single rupture. Compared with conventional blasting, DTB has a longer reaction time after initiation of approximately 200 ms, while conventional blasting has less than 0.2 ms, a difference of 1000 times. This indicates that DTB technology has a much smaller loading rate than conventional explosive blasting, resulting in a much smaller strain rate in the specimen than conventional explosives. Therefore, DTB technology eliminates the blasting crushed zone and makes it easier to achieve the desired directional fracture effect. DTB can achieve the ideal directional fracture effect under the conditions of a composite roof. The observation results of 10 roof-cutting holes within a 100 m test section on site show that the average crack rate inside the holes can reach over 90%. Therefore, DTB technology is expected to replace explosives and become a new type of directional pressure-relief technology for mine roadways. The research results contribute to revealing the mechanism of DTB and promote the application of DTB technology in the field of directional rock breaking.