This work introduces a nonequilibrium molecular dynamics method for calculating the mutual diffusion coefficient for mixtures. The method is based on the idea of the reverse nonequilibrium molecular dynamics algorithms, and artificially generates a mass flux through the Lennard-Jones mixtures by suitably exchanging particle positions and velocities in different regions. The analysis of the resulting steady-state concentration profiles allows the calculation of the mutual diffusion coefficient As a test, this method is applied to the calculation of the mutual diffusion coefficient of Ar/Kr systems, and reasonable results are obtained. At the same time, it is observed that the mutual diffusion coefficient strongly depends on the temperature and composition of the mixture. The method can be easily extended to other fluid mixtures and be adopted when studying the nonequilibrium fluid mixtures. (C) 2015 Elsevier Ltd. All rights reserved.