Abstract: A new concept，single fracture intrinsic permeability，was put forward through transforming cubic law expression. Then the equivalent intrinsic permeability of the series fractures and the parallel fractures was respectively discussed. The series-parallel model for forecasting permeability of fractured rock mass was presented based on the series-parallel relationship between fractures.  And，firstly，the concept of intrinsic permeability of fractured rock mass was put forward. In the paper，the series-parallel model and UDEC were respectively used to analyze a simple fracture network and the results were the same. The two theories are inversed in analyzing problems. However，the equivalent intrinsic permeability of fracture rock mass proposed by the series-parallel model can make it easier in practical application. The theory in the paper is also the basis for forecasting the coal mine water-bursting.

Key words: Single fracture intrinsic permeability, Equivalent intrinsic permeability, Series-parallel model for forecasting permeability, Discontinuous surface network flow theory