The study determines the abundance of zoobenthos in the rotational rice-tiger shrimp system. This study was conducted at Ca Mau province from January to June, 2013. Zoobenthos samples were collected with 4 times at 1water supply canal and 2 rice-shrimp systems stocked at 3 shrimp/m² density. Twelve zoobenthos species were found with polychaeta contributed 42% (5 species), following as gastropoda 32% (3 species) and others 8-17% (1-2 species). The differene of species composition of zoobenthos in canal (7±3 species) and two rice-shrimp systems (5±2 species) was not found. The composition of gastropoda class was no change during study period, while that of polychaeta class increased in the end of shrimp crop. The density of mean zoobenthos in the two rice-shrimp systems were the similar (425±333 ind.m^-2 and 464±338 ind.m^-2), but lower than that of inlet canal (700±157 ind.m^-2). Gastropoda density was the highest (78-94%) with dominance of Sermyla sp. species (Thiaridae family). Common species found were followed as Melanoides tuberculata, Sermyla sp., Thiara sp. (Gastropoda), Capitella capitata, Frabricia sabella and Nephtys caeca (Polychaeta). The mean Shannon-Weaver (H?) index in two rice-shrimp systems (H?=0.72 and H?=0.82) were lower than that of canal (H?=1.14). In the rice-shrimp system, although zoobenthos communities had a low diversity, zoobenthos densities had a moderately high.