Abstract: The dynamic change of siltation and erosion from May 1986 to October 1996 of the Yellow River mouth was studied supported by remote sensing and GIS. The results are as follows: 1. The current trend of the Yellow River mouth is that siltation tends to decrease and erosion tends to increase. Before January 1990 it increased by 24.9 km² per year and it decreased by 2.40km² per year after then. The northern and southwestern parts of the Yellow River mouth are main positions of erosion and the southern and mouth part are main positions of siltation. Also, the advancing rate of river mouth getting into the sea is decreasing obviously. 2. The area of the Yellow River mouth does not continuously increase as we studied before. Attention should be paid to the erosion of this region. 3. The reason of siltation decreasing and erosion increasing is the decreasing of water and sediment in the Yellow River, which caused by increasing use of the Yellow River water as well as the water and soil conservation in the upper reaches. In addition, the climatic change is one of the reasons, too.