In order to provide a basis for the prevention and control of water disasters in Baotashan aquifer of the floor in the study area, the physical, mechanical and water-physical properties of rocks with different lithologies at the bottom of the Yan 'an Formation were tested and analyzed by scanning electron microscopy, X-ray diffraction, disintegration test, mercury intrusion test, mechanical and hydraulic properties test. The sandstone had a composite structure of porous connected network, and the mudstone sample had a relatively dense structure. The quartz content of the rock was 56.2 % ~ 80.3 %, and the clay mineral content was 14.1 % ~ 34.7 %. As the particle size of the rock changed from coarse to fine, the quartz content gradually decreased, and the clay mineral content gradually increased. Mudstone had a certain resistance to disintegration, and the disintegration rate increased rapidly at 1~ 4 min, and the disintegration time generally did not exceed 10 min. The porosity of the rock was 5.11 % ~ 17.03 %. As the particle size of the rock changed from coarse to fine, the porosity gradually decreased. Sandstone belonged to medium hard rock, mudstone belonged to weak rock. The permeability coefficient, specific yield, water capacity and water holding capacity of coarse sandstone, medium sandstone and fine sandstone were much larger than those of siltstone and mudstone. Through the test and analysis of the physical and mechanical properties of rock, the significance of mine water prevention and control was given.  The results showed that finding out the physical and mechanical properties of the rock at the bottom of the Yan 'an Formation was an important work to analyze the threat degree of the lower coal group to the floor water disaster and to formulate the prevention and control measures, which could provide basic data and basis for the prevention and control of the water disaster in Baotashan aquifer.