All experiments in this study were carried out in a flume which was located in the hydraulic laboratory of technical faculty in Guilan University. The wave flume was 12 m long, 0.5 m wide, 0.5 m high and equipped with a wave-producing system and ultrasonic sensors. The objectives of current experimental study are to investigate sediment transport, bed formation and sustainability of sandy beaches with different grain size under tsunami attack. Sediment transport, caused by tsunamis, brings about severe damages to human beings, structures, beach topography and environment. Due to the devastating, destructive and scouring effect of tsunami waves, assessing their operation is of great importance. Experimental studies can be significantly helpful to evaluate the process of transported sediment by a tsunami. Three traps were employed to examine sediment transport in different parts of the beach. The achieved results indicated that wave breaking point has significant effect on the beach profile deformation and sustainability. Furthermore, grains with varying sizes, in the same conditions behave differently. As a result, for finer grains wave backwash has more effects on the sediment transport, while for coarser grains the wave itself has a main role in sediment transport.