Free-living marine nematodes were sampled and studied at a grid of 22 stations (from 32°29.35' to 37°0.56'N, 122°0.37' to 125°1.16'E) in the southern Huanghai Sea in January 2003. Nematode abundance varied from 50.5 to 127.2 ind./cm2 [(83.1 ±24.7) ind./cm2] at different stations, 80.1% of the total nematodes were in the surface layer (0～2 cm) of sediments. Two hundred and twenty-three species or taxa of marine nematodes belonging to 145 genera, 32 families and four orders were identified and first recorded in the Huanghai Sea. The common dominant species were Dorylaimopsis rabalaisi, Terschellingia longicaudata, Sphaerolaimus balticus, Metalinhomoeus longiseta, Quadricoma scanica, Prochromadorella sp., Paramonohystera riemanni, Marylynnia sp. 1, Vasostoma spiratum, Halalaimus spp.,Pierrickia sp.1 and Promonhysterafaber. Nematode diversity was correlated with sediment granularity. Pearson correlation analysis showed that Shannon-Wiener index had highly significant positive correlation with a sand content and negative correlation with a silt-clay content (P＜0.01); species richness index (d) had significant positive correlation with the sand content and negative correlation with the silt-clay content (P＜0.05). The diversity of the southern Huanghai Sea was lower than that in the center of Bohai Sea, but the dominance was higher.