The community structure, diversity and distribution of free-living marine nematodes were investigated in the first time in the coastal zone of Tra Co during December. 2008. Fifteen sampling stations were made a choice (from TC1 to TC15). Total 51 species of 43 nematode genera belonging to 17 families. 4 orders (Chromadorida. Monhys/erida. Enoplida and Trefllsiida) were recognized. Among them, the quantity of genera in family Chromadoridae represented the highest proportion with 10 genera. The proportion of Desmo,doridae was also high with 6 genera. The carnivorous and predatory nematode group (2A) dominated with 57.78 percent of total species. The nonselected deposit feeder group (1B) accounted for 5.61 percent, the predator group (2B) 35.30 percent and the selected deposit feeder group (JA) only 2.34 percent of total species. The Nematode biodiversity indices as Shannon- Wiener index (H') and Margalef index (d) were high at 5 stations (TC1, TC3, TC4, TC9 and TC15) and low at others. H' value fluctuated from 0.82 (TC13) to 4.04 (TC4).