Abstract: Based on the geological and hydrogeology data, it analyzed the background, cause, channel, and water sources of water inrush in No.118 working face. It obtained that roof separation space formed between Yijun group sandstone and underlying conglomerate and mudstone, water filling happened in this space from Luohe group sandstone aquifer, and it was the main water source. It proposed that water inrush accident of separation layer water could be prevented by destroying the closeness of separation layer and discharging separation layer water in advance.