Abstract: By virtue of field monitoring method，the variation law of ground pressure of roadways with change of excavation working space was explored with respect to pillarless sublevel caving，with Beiminghe Iron Mine taken as the engineering background.The radial force of roof，arch springing，and sides of roadways can be divided into three phases with advance of working face，which are stabilization，pressure-bearing，and unloading stage.As the distance between monitoring section and working face was greater than 15 blasting row spacing，the surrounding rock of roadway was in stable state and uninfluenced by the variation of mining space.As the distance was from 5 to 15 blasting row spacing，the surrounding rock of roadway was in the pressure-bearing stage，and the inflection point of stress started to appear within variation from 5 to 10 blasting row spacing，which means that rock mass deformation was intensified and uplifting of stress was accelerated.The radial force would be closed to the peak or in the both stages of peak and post-peak within the variation from 1 to 5 row spacing.The damage degree of rock mass is higher and its intactness is lower within thickness of 2 meters and 5 meters from working face，which are mainly caused by blasting stress wave and stress increment resulting from excavation.The research results provide theoretical basis with reasonable supporting and safety mining.

Key words: Impact of Mining Space Variation on Stope Ground Pressure with Respect to Pillarless Sublevel CavingPillarless sublevel caving, Ground pressure monitoring, Excavation space, Damage of roof