The velocity field in a single Plateau border (PB) of the aluminum foam in the drainage process is studied using a mathematical model for the flow inside a micro-channel. We show that the liquid/gas interface mobility characterized by the Newtonian surface viscosity has a substantial effect on the velocity inside the single PB. With the same liquid/gas interfacial mobility and the same radius of the curvature, the maximum velocity inside an exterior PB is about 6～8 times as large as that inside an interior PB. We also find a critical value of the interfacial mobility in the interior PB. For the values greater and less than this critical value, the effects of the film thickness on the velocity in the PB show opposite tendencies. Based on the multiscale methodology, with the coupling between the microscale and the macroscale and the results obtained from the microscopical model, a simplified macroscopical drainage model is presented for the aluminum foams. The comparisons among the computational results obtained from the present model, the experimental data quoted in the literature, and the results of the classical drainage equation show a reasonable agreement. The computational results reveal that the liquid holdup of the foams is strongly dependent on the value of the mobility and the bubble radius.