AbstractBased on qualitative and quantitative investigations of soil animals in nine sampling areas of the Yellow River Delta ( YRD) made from 1995 to 1996 and yearly investigations made in the same period of soil animals in three sampling areas of ancient , recent and contemporary YRDs , the species composition , dist ribution , seasonal changes and diversity of soil animals have been characterised. In the YRD ,38 species of soil animals have been identified ,most belong to the orders Acarina , Coleoptera and Collembola. According to different sampling methods , 19 species of large soil animals , 31 species of medium - small Tullgren soil animals and 3 species of medium - small Baermann soil animals have been identified. The species compositions and dist ributions in the three YRDs are different because of the age of soil formation. So are the seasonal species compositions and dist ributions , the soil animal in summer being richest in diversity. The index of diversity of soil animals in the YRD is correlated with the index of evenness , but is negatively correlated with the purity.