Abstract: To investigate the influence of load stress on gas permeability of coal rock and micro-visual flow of methane in raw coal, a series of numerical experiment were conducted to calculate changes in the permeability of simulated raw coal under various loading conditions by discrete element method program UDEC, and the results of numerical experiments were compared with lab study. The results showed that the numerical model was proved to be in good agreement with the results obtained from lab study. In rapid compaction stage, the stress which is applied to coal rock is less than 7.5 MPa and intensity of coal and rock, and the gas permeability of coal rock decreases with the increase of stress; in linear elastic stage, the stress is between 7.5 MPa to 15.1 MPa, and the closure of native crack is not significant, the gas permeability increasing with the stress is not obvious. In plastic deformation stage, the stress is greater than 15.1 MPa and the strength of coal and rock, and the secondary cracks are generated in coal rock and the gap width increases with the increase of stress, and the cracks with large flow appear in the coal seam, and the gas permeability increases rapidly with the increase of stress.