Abstract: In view of the problem that roof sandstone of coal seam is locally rich in water and affecting the working environment and production safety,the traditional gray extension correlation method was improved on the basis of modified resolution coefficient ρ.To evaluate the water abundance of Suntuan 10 mining area,four indexes including aquifer thickness,brittle plastic thickness ratio,core recovery and fractal dimension of fault were selected as evaluation factors.The results show that through improving distinguishing coefficient ρ by the method of variance method,can effectively avoid the interference caused by different values ρ;based on the extension model and the improved gray relational degree analysis method,the water abundance of roof sandstone in the study area is divided into four grades:weak,weaker,medium and strong.The weak and weaker water-rich regions have a wide distribution and large area,and the south is weaker than the north overall.The partition result is consistent with geophysical exploration and pumping test,and the calculation model established by this method has certain practicability.