Abstract: Based on 19 groups of injection pressure drop well test data in Luan mining area,the plane and vertical dis- tribution characteristics of modern in-situ stress in this area are systematically analyzed,and the control effect of mod- ern in-situ stress on coal reservoir permeability is discussed. The results show that the No. 3 coal reservoir in Luan mining area is a medium-low stress area as a whole,and the stress field types are vertically non-uniformly distributed. The stress field in the buried depth within 400 -610 m area is a strike-slip fault stress field( σH >σv >σh ),and the stress field in the buried depth within 610-800 m area is a normal fault stress field(σv >σH >σh ). The relationship be- tween pressure measurement coefficient of modern geo-stress field and burial depth in Luan area is 131. 67 / H+ 0. 165 9≤K≤544. 72 / H+0. 238 0,which is characterized by “shallow dispersion and deep convergence”. Coal reser- voir permeability is closely related to horizontal principal stress, horizontal principal stress difference and effective stress. There is a good power function relationship between the permeability of coal reservoir and the maximum / mini- mum horizontal principal stress and its stress gradient. The permeability of coal reservoir decreases rapidly with the in- crease of the maximum and minimum horizontal principal stress and its stress gradient. Horizontal principal stress difference affects permeability by controlling fracture opening and closing of coal reservoir. When the direction of maxi- mum principal stress in mining area is consistent with that of predominant fracture group in coal reservoir,the fracture in coal reservoir is tensioned and the permeability of coal reservoir is increased. When the direction of maximum prin- cipal stress in mining area is not in line with predominant fracture group in coal reservoir,the fracture in coal reservoir is squeezed and the permeability of coal reservoir is decreased. Therefore,the regional permeability between the Ergang Mountain and Wenwang Mountain faults is generally higher than that outside the Ergang Mountain and Wenwang Mountain faults. The permeability of coal reservoir decreases exponentially with the increase of effective stress. Under the same conditions,in areas with high coal reservoir pressure,the effective stress is low and the permeability is gener- ally high;in areas with low coal reservoir pressure,the effective stress is high and the permeability is generally low. The low pressure of No. 3 coal reservoir in Luan mining area may be one of the important factors affecting its low per- meability and low CBM production.