Abstract: The evolutions of the material interpenetration boundary induced by Rayleigh-Taylor instability were calculated under various acceleration histories using a buoyancy-drag model. It reveals that the development of mixing under constant acceleration is very different from that under variable acceleration. The calculation results were compared with detailed experimental data to prove the validation of the model. On the bases of these, a multiphase buoyancy-drag model was developed to study the mixing induced by Rayleigh-Taylor instability in dusty gases under constant acceleration. It is found that the mixing width decreases with the increase of the dusty concentration and the size of particles, which reveals that the particles in dusty gases restrain the development of mixing.