Abstract: In order to research the interaction between deep lower coal group floor mudstone and water in Daizhuang Coal Mine, through nearly two months of mudstone soaked with water, the conductivity testing, water-rock interaction before and after scanning electron microscopy and fluorescence analysis. Test results show that the resistivity of iron and aluminum mudstone soaking by water showed a rapid rising, rising slowly and steadily fluctuations three stages; iron mudstone and aluminum mudstone on the microstructure stucture showed loose, poor cementation, obvious holes. The conductivity change in iron mudstone and aluminum mudstone is mainly due to change in the content of pyrite and calcium carbonate.