Advection-diffusion apparatus was installed on a geotechnical centrifuge under 50g to run for 12 hours in order to investigate migration of Cl- in clay-bentonite barriers. Analytic solution was used to calculate the diffusion parameters. The scaling requirement was studied. The prototype of the centrifuge test was simulated by commercial software and the scale law of solute migration in geotechnical centrifuge was discussed. Efficiency of the tested clay-bentonite barriers used as an amendment measure in an old landfill to prevent pollution was analyzed by numerical simulation. In the centrifuge test, the actual advection velocity and the Péclet number calculated from outflow are smaller than the critical values. Mechanical dispersion can be neglected and the consistent scaling law can be satisfied. Breakthrough has not happened after 3.42 years for the simulated layer with a prototype thickness of 2.5 m and the hydraulic heads of 5 m and 10 m. Saturated hydraulic conductivity and effective dispersion coefficient of the tested soil are 8.5×10-8 cm/s and 7.82×10-7 cm2/s, respectively. Numerical simulation of the centrifuge test prototype shows that under a centrifugal acceleration of ng, solute migration under advection and dispersion in the prototype can be modeled in the centrifuge in size and time. If the tested clay-bentonite is used in old landfills for amendment of early barriers, the migration can be significantly slowed down and the requirement of pollution control can be satisfied.