The hydrodynamic conditions of the dam group flooded by the tidal estuaries are complex and changeable,and the complicated flow structure of the spur dikes field determines the siltation process and the form of siltation in the field.Taking the field formed by the spur dikes at the north passage of the Yangtze estuary for example,we analyze the deposition pattern,rate characteristic and regularity of the dam field after the dam formation.The result reveals that with the passage of time,the dam within 2 m isobath gradually closes to 0.2 times the distance from the dam head dam strengths,and 5 m isobath gradually closes to the dam at the head of the dam;there appears a logarithmic relationship between the initial volume of the dam field and balance volume at the scour sedimentation equilibrium;when the groin spacing is 3 to 4 times the length of dam,dam deposition distributes in equilibrium;the inflection point appears 5-6 years after the dam formation.Moreover,the causes of the siltation characteristics in the dike field are discussed in terms of the layout parameters affecting the silt dam.