Abstract: Based on a generalized tortuosity model and a cubic unit cell topology, an analytical model is developed for predicting the permeability of open-cell metallic foams. The present model has a simple form and requires no fitting or empirical parameters. It is capable of analytically predicting the permeability of open-cell foams over a wide range of porosities (0.55～0.98) and pore densities (5～100 PPI), with good agreement with experimental data. Results demonstrate that the flow tortuosity determined by algorithm branching method enables faithfully capturing the behavior of fluid flow across open-cell metallic foams. Further, the modification made by open pore rate successfully extends the present permeability model from fully-open foams to semi-open ones.