Air permeability is an easy but important soil parameter, which can be used as an indicator of Ks at field scale and of soil porosity and soil structural property. So far lots of air permeability models with different properties have been established. This paper compared the constant pressure method and the transient-flow method in measuring air permeability in the measure efficiency andeconomy, the range of relative error of measured result. Comparing to the constant pressure method, the transient-flow method is unnecessary to measure the air quantity through the soil sample, and it cost less time and need only a small volume air going through the sample soil, thus cause less damage to soil sample structure. The constant pressure method embraces the advantage in technique maturity and calculation convenience. The indoor measurment results of 60 soil samples showed the extremely significant correlation between the two methods (y = 0.979 1x), taking the constant pressure method as a standard, the range of relative error of the measured results between the two methods was between 0.5% - 45%, the relative error was less than 15% for more than 80% of measured results. Meanwhile, the test results confirmed the significant linear relation between gaseous conductance rate Q and the gas pressure value △P within admeasuring apparatus by constant pressure method as well as the linear relation between time T and the dynamic change of seal section pressure in the measured soil sample by constant pressure model proposed by Kirkham.