Abstract: According to the mining technical conditions of the large-diameter long-hole sublevel open stoping with subsequent filling method for a copper mine in Anhui province，it is calculated that the reasonable width of isolated pillar is about 20 m with pillar safety factor formula，and the reasonable span of isolated pillar is 60～65 m with beam balance theory in material mechanics.Based on the theoretical calculation，three plans are adopted to analyze the stress and displacements under different stope spans in numerical simulation.The result shows that when the width of isolated pillar is 20 m，the roof and floor of stope are being pulled while the isolated pillars are being pressed after excavation，the stress and displacements increase with the increasing of isolated pillar span.Especially when the isolated pillar span reaches 70m，the stress and displacements of stope increase apparently with the greater shear destruction of the isolated pillar，and the roof safety factor is less than 1.So，it is reasonable to set the span as 65 m for the isolated pillar，and this result is in line with the mine actuality.

Key words: Open stoping with subsequent filling method, Isolated pillar, Reasonable span, Numerical simulation