Abstract: The characteristics of the weathered zone in bedrock above seam roof determine the water-resisting capacity of the zone.Through the research on many factors of bedrock weathered zone of the roof of seam 7₂ in the working surface 7₂11 in Suntuan coal mine,such as lithological characteristics,mineral composition,physical properties of water,physical and mechanical properties,weathered zone distribution characteristics,etc,it is showed that the minerals of rock fragments in bedrock weathered zone mainly consist of quartz and feldspar,that paleotopography has had obvious impact on the variation in thickness of the weathered zone,and that the weathered zone has certain watertight performance and restrains carving zones and transmission fissure zones from developing upwards.This kind of watertight performance is very advantageous to the reduction of safety pillars under water bodies,and it has important and realistic significance in reasonably setting up the height of coal and rock pillars for safety and the upper limit of mining,increasing the recovery rate of coal resources as well as fully developing and utilizing coal resources.