Abstract: To couple continuous and discontinuous analysis methods for the stability analysis of surrounding rock in underground power stations, a rapid calibration method for mesoscopic parameters based on a soft-hard mixed parallel bond model was implemented.This method can quickly correspond to the given rock macroscopic mechanical parameters to PFC model mesoscopic contact parameters.A three-dimensional discrete continuous coupling analysis model for the tail-race surge chamber of Xulong Power Station based on the coupling of particle discrete element PFC 3D and finite difference FLAC 3D was constructed.The macro-micro deformation and failure characteristics of rock pillars between tail-race surge chamber caverns during excavation were studied, as well as the impact of lateral water pressure on the rock pillar stability.The results showed that the deformation and stress increment of surrounding rock caused by the water pressure in the surge chamber under maintenance condition were minimal, but there was a plastic penetration zone at the height of 22.7 m in the upper half of the rock pillar between the caverns, with poor local stability.Thus it is necessary to carry out a special support scheme study on the plastic penetration zone of the tail-race surge chamber and tail-race branch tunnel rock piers during the construction period to ensure the safe construction and operation of the Xulong Power Station project.