Mechanics of sediment transport is a branch of basic technical science in which the process of erosion, transportation and deposition of sediment take place under action of gravity, flowing water, wave and wind. The theory of mechanics of sediment transport was developed and the main frame of the science was constructed in 1940s and 1950s. Thence less great breakthroughs were made. Now development of technology and accumulation of knowledge have pushed the science branch at a scratch line for a great leap. Four main directions of the sediment research are: (1) Sediment transport in unsteady flows. The main theories and formulas of sediment dynamics were established based on steady and uniform flows. Nevertheless, the theories and formulas often fail to apply in engineering projects because sediment in nature is transported by unsteady and non uniform flows. It is more often so following development of the application scope and requirement of high accuracy estimation of rate of sediment transport. There is an urgent need for knowledge of sediment transport and river deformation in unsteady flows. (2) Development of boundary sciences. Boundary sciences develop from combination of sediment transport with other sciences, such as a combination with geomorphology created dynamic geomorphology and a combination with environmental science initiated environmental sedimentology. The wet land science is a combination of hydrology, sediment transport and biology. (3) Macroscopic studies. Microscopic studies have revealed the mechanism of grain motion. Macoroscopic studies, on the other hand, can provide a different approach to the dynamics of sediment motion and its result geomorphological evolution. Remote sensing and Geographical Information System will promote macroscopic studies. (4) Computer modelling. Computer modelling have been widely used to solve engineering problems. Two and three dimensional models will be widely used in a seeable future. About 20 new problems, which will possibly become the main growing points of the science, are listed in the paper, for instances, defining the speed of the river motion as the volume swept by the river in unit time. The “force” inducing the river motion is instability of the sediment carrying capacity and oncoming load. An equation of motion is yet to be found and the law of the river motion to be studied. Sediment researchers and engineers have proposed many formulas for bed load transport rate and suspended sediment carrying capacity of flow. Nevertheless, there is no formulas to calculate rate of sediment scour. Studies on this problem is urgently needed for designers of oil pipeline beneath a river bed. Other problems include dynamics of debris flow, dynamics of river mouth shrinkage, sediment transport capacity of sea currents, land creation and delta dynamics, sediment budget, role of sediment in pollutants migration, river decontamination, modelling of wetland development, artificial hyperconcentrated flow, effect of variation in land use on sediment yield and motion, effect of river training and renaturalization, et al.