Abstract: Coal mining under the river is one of the problems.This paper,Tianzhu coal,for example,predicts the ground deformation by the use of 3D probability integral method and the influence on Jinsha River after 3229 is in phase presumed to be excavated.And then the water flowing fracture height is predicted based on deformation analysis,which is compared with that is calculated by the formula.With the mining process,water flowing fractured zone may break into fissures in the Jurassic pore confined aquifer and the mine discharge will increase,which may lead to the Quaternary alluvium aquifer water above diving or poured into the underground tunnel through the cracks caused by subsidence submergence.Measures should be taken to avoid water infiltration and to prevent underground flooding when coal mining under the river.