Tidal flat formation on the coastal peat is a unique phenomenon that has occurred at western part of Bengkalis Island, Riau Province, Indonesia. It was identified that coastal erosion problems have been occurring continuously during at least the last 30 years along the north part of Bengkalis Island. The materials have moved to the south part of Bengkalis Island, and sedimented as tidal flat. Research on tidal flat in the peatlands has not yet been developed, so this study aims to carried out an experiment study in order to understand the tidal flat formation on coastal peat. The method used in this study is a simulation of tidal flat formation with several wave variations. Simulations were carried out using laboratory experiments with coastal peat samples and sea water at the wave channel. The results show that the waves and the velocity greatly influence the tidal flat formation and its formation rate. In addition, the formation of peat tidal flat was also influenced by velocity settling of the peat particles. The energy for tidal flat formation was the minimum energy generated by waves, that cannot transport the particles move back by reverse flow.