Beixinyao Mine is in construction, there is floor water burst in +1 040 mlevel south wing return air roadway mining, the maximum water inflow reaches 455 m3/h, the position is considered as safe area by water burst coefficient method, which shows the method alone is not precise enough to evaluate the geological condition. Based on the sufficient analysis of coalfield geological condition, by analyzing the factors affecting floor water burst like inrush floor damage depth, bottom layer thickness, water distribution and effective protective thickness, etc, five figure double coefficient method is applied to evaluate the floor Ordovician limestone, the prediction result provides reference for water prevention and control.