In recent decades coal mining conventionally has been excavated by longwall method. Before exploitation, the environment remains in perfect stress balance. Environmental fluid such as gas and underground water in non-permeable layer of clay at equilibrium, are trapped. The turbulence of stress during longwall mining caused to making voids and disruption of ground insitu stress. In continuation fractured damaged zones of the rock mass dehydration is occured, and followed by gas emissions from coal layers during pore pressure droping. Discharging of stress and fractures associated with exploitating, provides new paths for flowing methane into excavations. The scope of this study is involved investigate the effect of redistribution of stress on factors in the gas-riching in coal layers during excavating, maintenance and destruction across longwall. Morever, to estimate insitu stress as the most important factor to be considered. Due to lack of comprihensive rock mechanics studies and in-situe tests to assest the in-situ stress field components in Parvadeh region locating in Tabas coal mining and needing the calculation the amount of stresses and geomechanical properties of discontinuities, the geomechanical parameters of faults and amount of stress, Using the mechanism of faulting and amounts of occurred displacement values of faults, using the finite difference software code FLAC 3D with the use of direct back analysis method is specified. The result of modeling suggests the optimal value 0.3 as ratio of vertical to horizontal stress, that by this ratio of stresses, the optimal parameters of geomechanical discontinuities were obtained. The three-dimensional design of discontinuities, as well as layering, to avoid simplifying assumptions for numerical modeling in regards to setting off flat discontinuious planes and using the their infinite length in model, the industrial design software Rhinoceros was conducted. In this regard, the lack of information of destruction material zone, using numerical and conforming with Salamon analytical method, the characteristics of destruction material zone for different heights of destruction was determined. The results of the stress distribution on the confining tunnel zone show that in a situation where the maximum stress is perpendicular to the axis roadway, In front of working face there isn’t any stress concentration and permeability in the axis hallway direction i reduced. The evaluation of performance of maintenance while excavating, maintenaning and destructing of zone, it’s be turned out that the anchor stresses of both sides of working place, before the passing of a certain drilling step, are be formed. The stress conditions in working face in regards to distance of working face, indicate the asymmetry of stress components that it’s be originated as the pre-failure of the rock mass and the influx of gas into the working face. In accordance with the direction of the principal stresses on faults and inherent fracture system in coal, consistent with increased levels of stress and methane pore pressure with depth, methane-enriched zone was set at the entrance to the main roadway. Modeling drilling, maintenaning and destructing of methane-coal zone in hydromechanization accompanied suggest that pore pressure changes continue along a distance of about 4 meters in front of the mining working face, and then change of pore pressure with a dropping rate is falled. The changes of pore pressure are followed by Klinkenberg’s law that expresses the dependence of the gas permeability and fluid pressure. The volume of released gas also is in accordance with the used adsorption isotherm that is followed by changes in pore pressure of gas fluids.