It is the first time the benthic water quality of the Sai Gon River was investigated according to the ABC curve method based on the analysis of the density and biomass of all species of free-living nematodes that were present in the sediment of the studied area. The nematode samples were collected in the Sai Gon River from Cu Chi district to Navioil port during 2014-2015 at dry and rainy seasons. Our results showed the benthic environmental quality was not homogenous in during four times of sampling and at different stations. While some stations were heavily polluted in all sampling times such as Bien Dong port, Lotus port, and Navioil port, but some other stations were polluted only in the wet season such as Tan Thuan Dong port, Ben Nghe port, Sai Gon New port, and Sai Gon Shipbuilding port. And Ben Nghe port, Vietnam International Container Terminals - VICT port, Sai Gon New port, and Sai Gon Shipbuilding port were moderately polluted in the dry season. In the rainy season, Ben Duoc - Cu Chi port, Tan Cang port, Ba Son Shipyard, and VICT port were lightly influenced.