Based on the correlations between charge and space of boreholes of blasting in rock, the initiation mechanism of fracture zones was studied according to theories of explosion and rock mechanics. The scopes of crush zone and crack zone, in a condition of decoupling charging, were calculated. The correlation between explosion gas pressure and scope of crack was put forward, and the contradiction between charge and space of boreholes was solved theoretically. The blasting experiments in field were carried out and the experimental effects are satisfactory: shattered blocks are small and smooth face is well shaped. For a tunneling cycle, explosive cost is decreased by 17.8% and the single footage is increased by 0.2 m; the rates of half-hole marks of perimeter holes and the non-smooth grades of the cut contours are more than 92% and are less than 100 mm respectively. The results will provide parameters for blasting design and engineering practices with the theoretical gists.