Molecular behavior of a nano cluster in a nano scale flow field was investigated by the classical molecular dynamics method. A tiny butane molecular cluster and an aluminium surface were employed to simulate the interaction processes of a nano cluster and a metallic filter. The velocity of the butane molecules affected their behavior of passage or adhesion to the filter. The butane molecules adhered to the upper layer of the filter in the cases of small velocity and they adhered to the bottom of the filter in the cases of large velocity. The cluster passed though the flow of the filter in the cases of very large velocity.