With the expansion of the scale of underground engineering construction,it becomes an important issue about seepage failure hazard of fractured rock mass in engineering and theoretical circles. Developed with simulated rock rough single fracture specimens of different rock joint roughness,laboratory tests of non-Darcy seepage in rough single fracture with variable apertures and high hydraulic gradient are carried out. It is indicated that flow behavior in the rough fractures becomes nonlinear with the high seepage velocity,and the hydraulic gradient and volumetric flow rate data points are fitted very well by the Forchheimer equation. A semi empirical formula of the non-Darcy effect coefficient is presented,which provides an important reference for the prediction of water bursting in engineering practice.