The assemblage structure of harpacticoid copepods inhabiting the soft sediments of littoral and sublittoral areas of Cat Ba archipelago (South China Sea) is analysed. Three basic types of harpacticoid taxocenes were observed in the upper sublittoral. Main dominant species of taxocenes were Amphiascoides sp., Stenhelia latioperculata, Paramphiascella sp., Phyllopodopsyllus sp., Tisbe sp.1 and Amphiascoides sp. In addition, the main characteristics of harpacticoid species composition in littoral rock pools are described. A comparative analysis of shallow-water harpacticoid communities from different biotopes of the tropical region is presented, and shows that harpacticoid diversity and abundance are lowest in muddy sediments. Highest diversity and abundance are found in washed sands and silty sands with detritus. In general, the structure of muddy bottom communities is the most homogeneous throughout the tropics. Mangrove forests have no significant influence on harpacticoid taxocene structure. Harpacticoid associations of washed sands and silty sands with detritus demonstrate greater diversity and are region-specific.