In order to find out the impact of dumping dredged materials on Lanshan Port Temporary Ocean Dumping Site areas, with the methods of single factor index and eutrophication index,we evaluated the monitoring data of the seawater and sediments quality over years, and analysed the changes of marine biology and the water depth. The results show that the water quality of the investigated areas reached the secondclass water quality from The Chinese National Standard of Seawater Quality. In addition to inorganic nitrogen, other quality indices of the evaluation factors are generally more stable, fluctuate within a certain range. The sediment quality of the investigated areas reached the firstclass sediment quality from The Chinese National Standard of Sediment Quality, and the sediment quality indices of the evaluation factors fluctuate within a small range. Dumping dredged materials caused a temporary reduction in the total density and the total number of phytoplankton species. At the same time dumping dredged materials caused an obvious raised topography in the north and east area of the Lanshan Port Temporary Ocean Dumping Site. The results show that except the water depth had been impacted, the dumping of dredged materials has not caused significant impact on the ecological environmental quality of Lanshan Port Temporary Ocean Dumping Site areas.