Abstract: Along with coal exploration’s being expanded into deep-burial strata in Eastern China,floor water inrush accidents of Ordovician limestone occur often,which cause serious casualties and property losses.Scientific research of water inrush quantity prediction benefit to safe mining and water disaster control.This paper used derivation of the finite-difference equation for Ordovician limestone aquifer water heads,which were solved using the finite difference method based on generalizations of the Xin’an Mine’s hydrogeological conditions and three-dimensional flow numerical simulations using Visual MODFLOW.The simulated water levels were verified and calibrated by actual observation data for the entire hydrological year from March,2011 to February,2012;the errors for each period were all less than 11%,generally around 4%.The Ordovician limestone aquifer water quantity in water inrush danger area was calculated according to the simulated levels is about 1 150 m3/h.The results show that the prediction of water inrush quantity is quite similar to the severe water inrush of 1 244.3 m3/h that occurred in 1995 in the same place.The prediction result is accurate.