Abstract: Before a tunnel excavation, the groundwater in the rock and the surrounding rock stress are in a state of relative balance, because the excavation makes tunnel groundwater drain has a new channel, thus accelerating the water cycle, which destroyed balance of the original supplies-migration-the drainage system;On the other hand, the surrounding rock stress was redistributed and part of structural surface was closed due to pressurization, part of unloading rock mass produced shear slippage, which vandalized the original groundwater seepage condition, thus making tunnel itself become an underground corridor to discharge water in different forms, resulting in bursting water disasters.Monte Carlo method was used to establish 2-d discrete-fracture network, which was input rock mass structure discrete fissure network medium model(DFN), according to the model of the discrete element method in fractured rock mass seepage characteristics, fracture rock cavern excavation mechanical characteristics and seepage stress coupling mechanism of fractured rock mass.Combined with concrete examples, a comparison was done for cases of excavating caverns in fractured rocks with and without consideration of hydraulic coupling.