Abstract: Heights of roof strata "two-zone" should be measured for each new coal mine. To determine water flowing fracture zone height of the first mining face roof in Gaojiabu coal mine comprehensively, three methods including injection water leakage measuring in upward slant holes, underground-ground joint microseismic monitoring and numerical simulation with UDEC were applied. Similar fracture zone height values which are 88.03 m, 86.54 m and 87.00 m were detected by three methods near the working face stop line. Combined with injection water leakage measurement in underground upward slant hole or surface borehole, strata deformation and failure time-space four dimensional characteristics can be monitored by the underground-ground joint microseismic method which has outstanding advantages in analyzing the changing rule of the fracture zone height.