The area of seagrass distribution in Sanya bay reduced greatly in recent years. In order to make clear the reason of
seagrass decline, the relationship between seagrass distribution and land use change in Sanya Bay was retrieved in the
paper, Landsat TM and ETM+ data of 1991, 1999, in situ observation of seagrass distribution and water chemical indexes
were used to retrieve the information of land use change, seagrass distribution and water quality status in Sanya bay.
From the satellite images, area of eastern and western Sanya Rivers reduced in 1999 compared with that in 1991.
Seashore land use change detection showed that the shape of costal line at the northeast of Lu Huitou peninsular changed
greatly. Corresponding to land use change, the area of seagrass distribution in Sanya bay decreased, from distributed in
the great part of south coast in 1991 to less than 1 hectare in southwest coast of Sanya bay in 1999. The effect of land use
change on seagrass distribution can be concluded as following: seagrass distribution in Sanya area conversely correlated
with land use change, the more area of land use change the less coverage of seagrass distribution. Mainly because of land
use change changed the water quality and sediment type.