During 2007-2013, the fauna of free-living marine nematodes in Red River Estuary and its mangrove forest had been investigated. 107 species belonged to 52 genera of 23 families of 8 orders were nized
among them one genus and 10 nematode species were described as the new species for. Family Xyalidae was the most abundant in species composition and in individual density
the nematodes was family Leptolaimidae, the third and fourth places occupied by families Desmodoridae and somatidae and the last was family Chromadoridae in both seasons. Nematodes that occurred inantly in both dry season and wet season were following species: Daptonema paraoxyuroides and Sphaerotheristus validum Gagarin, Nguyen Vu Thanh, 2005
Sphaerolaimus maeoticus Filipjev, 1922 Terschelligia lissa Timm, 1962.