The invention discloses a porous media air permeability estimating device which comprises a high-pressure air cylinder, a test specimen clamping assembly and a monitoring display, wherein the test specimen clamping assembly comprises an upper clamp and a lower clamp which are connected with each other and are hollow cylinder bodies communicated with each other; the joint of the upper clamp and the lower clamp is provided with a gasket, the top end of the upper clamp and the bottom end of the lower clamp are respectively provided with an upper air hole and a lower air hole, the upper air hole is connected with the high-pressure air cylinder through a first air pitometer, a pressure gage and a reducing valve successively, and the lower air hole is connected with the monitoring display through a second air pitometer and an air flow sensor successively. The porous media air permeability estimating device provided by the invention has the advantages that the operation is simple, the testing precision is high, the sealing effect is good, the purpose of testing porous media with different air permeability properties such as low permeability or high permeability in parallel is realized, test errors are greatly reduced, and the reliability and comparability of testing results are improved. The estimating device can be also used for estimating the air permeability of the porous media in a quantitative and qualitative manner.