Abstract: In order to make the grout flow more visually in the crack network of the coal and rock mass, the introduction of the stress strength factor was applied to discuss the broken criterion of the crack tip, the crack expansion orientation and expansion length under the pressure shear and tensional shear status and to analyze t he flow spreading law of the grout within an unitary crack. Based on the circumstance, the FORTRAN language was applied to write and prepare the flow expansion pro gram of the grout within the non-connected crack network. Taking the mine grouting project as an example, the program was applied to simulate the spreading scope of t he grout in the crack network under the different grouting pressure. The simulation results showed that the spreading of the grout would be disproportional.The higher of the grouting pressure, the easier splitting the crack tip would be and the longer the crack expansion would be.Under the certain grouting pressure, the secondary cracki ng and other cracking could be connected to each other and the grout could flow continuously.When the grouting pressure was 4.0 MPa, the comparison analysis betwe en the porous medium theory calculation, the program simulation and the site exploration showed that the simulation results of the program and the actual site grouting could be well ftted.