Salt marshes in estuarine and coastal zone play a key role on erosion control and coastal protection for their attenuating wave height and dissipating wave energy. In this study, we selected three typical salt marsh species: Spartina alterniflora, Phragmites australis, Spirpus×mariqueter in Changjiang estuary to measure the capability of attenuating and dissipating wave with selflogging wave sensors and Trimble GPS. Six sampling lines offshore and three sites on each transect with the pattern of “mudflatsalt marsh frontiersalt marsh” have been set up. Wave attenuation onshore in terms of significant wave height and wave energy have been analysed through 19 tidal periods with three salt marshes distribution patterns. The results show that: 1) The capability of coastal protection in typical salt marshes ranks with an order Spartina alterniflora＞Phragmites australis＞Spirpus×mariqueter. They attenuated 80% of wave heights (average) and dissipated 90% of total wave energy (average) as the wave crossed over the Spartina alterniflora 30m wide, or Phragmites australis 40m wide, or Spirpus×mariqueter 185m wide. 2) Vegetation density is the crucial factor for coastal protection which affected by plant characteristics, plant height, bed gradient, wave action and so on. There was obviously polynomial relation between Spirpus×mariqueter width and wave attenuation, exponential relation between Spartina alterniflora width and wave attenuation, logarithmic relation between Phragmites australis width and wave attenuation.

Key words：salt marsh; ecological function; coastal protection; wave attenuation; the Changjiang estuary