Abstract: A method of enteromorpha prolifera monitoring using moderate resolution environm ent satellite data is proposed. Based on the spectral characteristics of enterom orpha prolifera, remote sensing methods and processing procedures are established and then the monitoring results are derived. With the support of GIS technique, the affected range, extent, moving path and coverage of enteromorpha prolifera can be developed and relevant products are produced. During the marine alga catchi ng campaign, enteromorpha prolifera monitoring products are made and provided to the campaigners in time. These products help to find enteromorpha prolifera are a promptly and are highly evaluated.The monitoring results show that enteromorpha prolifera in the Yellow Sea appear s in mid May of 2008 at first, and then the range of enteromorpha prolifera expand grad ually and move northwestward. In mid June, enteromorpha prolifera influence the region of Yellow Sea near Qingdao Olympic regatta sea area and the size reaches up to 800 km². With the progress of a massive algae clearing activity, the ra nge of enteromorpha prolifera decreases rapidly. In mid July of 2008, there is little e nteromorpha prolifera in Qingdao Olympic regatta sea area.The temporal and spatial distribution characteristics of enteromorpha prolifera from 2006 to 2008 are analyzed using multiple observations of EOS/MODIS data and t he result shows that there are no evident phenomena of enteromorpha prolifera in Yellow Sea in the summers of 2006 and 2007.The coverage map of enteromorpha prolifera accumulated from multiple observation shows that high density enteromorpha prolifera appears most frequently in the o ffshore area and the sea area about 100 km south of Qingdao. About more than 200 00 km2 of sea area is influenced by enteromorpha prolifera in different extent in the summer of 2008 altogether.The moving path of enteromorpha prolifera induced from the multiple observation from May to July of 2008 shows that enteromorpha prolifera moves from southeast to northwest. It can also be concluded that enteromorpha prolifera moving path is deeply influenc ed by the wind and ocean current.