Based on changing stress state, mining of deep soft rock roadway was difficult and film, the roof and the bottom drum were always occurred, which was hard to explore distribution of secondary stresses. FLAC3D numeral simulation software was used to analyze stress variation of surrounding rock of roadway floor. No.2 coal roadway was taken as an example, necessary supporting measures were took after mining No.2 coal raodway to monitor size of drum in bottom of lane, and graph was synthesized by least square method, which was proved by practice that the curve was fully consistent with actual bottom drum in No.2 coal roadway.