The present paper reviews the researches in the formation mechanisms of the estuarine turbidity maximum.The turbidity maximum play a very important role in mud transport in estuarines. It is typically present in partially to well-mixed estuarines. Though its formation had been contributed mainly (even solely) to the trapping mechanism caused by the vertical gravitational circulation in estuarines, a turbidity maximum may be generated by following proceses: the settling and scouring lag effect, the flocculation,the estuarine circulation,the stokes drift,the tidal current and the resuspension of bottom sediments.Eeither of the six generation proceses may be predominant in estuarines of different hydrodynamic regimes. Their predominance is controlled by the equilibrium between the tidal and riverine dynamics.Thus the estuarine comparision and the mechanism study are the inportant toics in the estuarine mud transport research.