1. In the Nematoda, the sexes are separate and the males are generally smaller than the females which lay eggs or larvae.

2. Results show that in the region, Nematoda was the predominant group, and Acarina, Collembola, Tardigrada and Harpacticoida were common groups.

3. The community structure of benthic nematoda in Tianjin offshore area was analysed with the multivariate statistical method. A total of 15 stations were arranged for nematoda sampling.

4. With the increasing of Acetochlor concentration, the Nematoda population significantly reduced, so Nematode was used as one of bioindicators of changes in agroecosystems.

5. Small - middle size soil animals belong to 5 phylum, 6 class, 9 order, 7 famility. The dominant groups is Nematoda.