Abstract: The variation Poisson’s ratio was obtained by comparison between the results of two measuring methods.The variation of axial strain-radial strain curve under different cell pressures was similar.The tangential Poisson’s ratio changed from 0.2 to 0.3 under the initial loading,and reached 0.5 at very small strain.The tangential Poisson’s ratio of local deformation varied faster than that of the traditional full deformation measurement and the average value of the former was larger than that of the latter.The tangential poisson’s ratio of soil increased when the principal stress ratio increased.When the principal stress ratio reached a certain value,the increment of tangential Poisson’s ratio would be larger than 0.5.It was reasonable to establish the relationship between the Poisson’s ratio and the principal stress ratio.