According to geological data of Xiaoweigou Mine and analysis of its hydrogeological conditions, the hydrogeological conditions with pressure of Ordovician limestone water were evaluated by water inrush coefficient method and safety head pressure method. It was inferred that the Ordovician O2f+O2s water level elevation was 525.50-527.50m, the minimum of No.9, 10 and 11 coal seam floor elevation was 440m in the south of minefield, which was lower than the Ordovician water level and belonged to partial pressure mining coal seam. Maximum water inrush coefficient of No. 11 coal seam was 0.047 MPa/m through calculation, which was less than 0.06 MPa/m critical value. Meanwhile, 30 m range on both sides of fault in pressure zone was used as an outburst danger area; safe head pressure calculation method was used to evaluate Ordovician limestone water in stope working face. The calculating results showed that water pressure of floor isolation layer was less than safe water pressure.