In order to research on the issue of high-pressure gas blasting fracture deeply, a high-pressure gas blasting cracking experimental system was established; the effects of gas pressure and gas volume on the morphology of crack growth were studied; the p-t curve of pressure in the blasting process with time was obtained; and the mechanism of high-pressure gas blasting cracking was analyzed in this paper. The conclusion has shown that the stage of effect of high-pressure gas blasting on the test block includes three stages: the gas jet impact stage, the crack initiation and development stage, and the perforation fracture stage. In the design of gas pressure of 5 MPa, the experimental block only produces one longitudinal main crack. As the gas pressure increases to 7.5 MPa and 10 MPa, besides forming one longitudinal main crack, a transverse main crack is formed with further expanded 4-6 secondary cracks. In the same design of gas pressure regardless of volume size, each pressure variation stage has the same length, and the experimental block of the cracking pressure is basically the same. With the higher design pressure, the cracking pressure and the fracture pressure are higher. In the same design of gas pressure, with the larger gas volume, the fracture pressure required for the experimental block is smaller.