Abstract: Based on the comprehensive and systematic investigation and monitoring results made from 1996 to 1998 of environmental quality and biodiversity in the Yellow River Delta (YRD),the environmental quality of the atmosphere,rivers,reservoirs,lakes and shallow sea beach lands in the area has been studied,and so have the diversities and their features of marine living things,fresh water living things,terrestrial and island higher plants and terrestrial animals.Their damage state and causes have also been analyzed.In addition,the countermeasures for protecting biodiversity and the way for its sustainable use have been put forward.The results obtained are as follows:in the sea areas near the YRD have been identified 116 species of phytoplankton,79 species of zooplankton,222 species of zoobenthos,192 species of intertidal zone animals,112 species of fish and 11 species of other marine animals;in the fresh water areas 291 species of phytoplankton,144 species of zooplankton,69 species of zoobenthos and 102 species of fish;and in the land and island areas 608 species of high plants,922 species of invertebrated,and 325 species of vertebrates,4 of them are new records in Shandong Province.In the wetlands of the area there are diverse vegetation association,rich bird diversity,many key protected bird species and large numbers of sub-populations.