Abstract: A device is developed for measuring the gas slip factor b and intrinsic permeability K_∞. The theory of operation is based on a new method of measuring the gas permeability K_g. By this method，many timepressure data points are measured during the process in falling of pressure, thus，several data of K_g are calculated, and after that, the gas slip factor b and intrinsic permeability K_∞ can be obtained by the way of least squares. A test to the repeatability shows that the device works reliably.

Key words: slip factor, gas permeability, intrinsic permeability, Darcy′s law