Sediment transport is a geophysical phenomenon in which sediment particles are driven to move in streamwise and vertical directions by various forces. Almost all existing formulas of sediment transport were derived without considering vertical flows V, resulting in a large discrepancy between measured and predicted transport rates, as has been reported in the literature. This paper investigates the effect of vertical motion on sediment transport. It was found that upward fluid velocity increases particles' mobility, and downward motion increases particles stability. Furthermore, the investigation showed that decelerating flows can promote upward flow and vice versa. New equations were developed to express the influence of vertical motion on sediment transport. A reasonably good agreement between measured and predicted sediment transport rates was achieved.