Abstract: The secondary pollution of contaminated soil can be controlled by permeability reduced and evaluated by obtained hydrodynamic dispersion parameters. It is impossible to obtain hydrodynamic dispersion parameters of contaminated soil with low permeability by the existing column tests and methods. To solve the above problem, the breakthrough curve is obtained by the improved flexible wall permeameter. Based on the breakthrough curve, the hydrodynamic dispersion parameters of contaminated soil can be calculated by numerical inversion. The results show that the hydrodynamic dispersion parameters of contaminated soil with low permeability can be determined by means of the flexible wall permeameter and numerical inversion method.