Kien Giang is a province in the Gulf of Thailand with great potential for mariculture. We have conducted a study on the zooplankton fauna at Kien Giang sea to collect the latest data, then there is a basis for analyzing, evaluating and making comments and recommendations to contribute to sustainable mariculture in this area. We conducted two surveys in April, 2021 (dry season) and October, 2020 (rainy season). The zooplankton samples were collected from 33 sites in the Kien Giang sea, using plankton net (with mesh size of 120 µm, mouth diameter of 40 cm attached oceanics mechanical flow meter) to pull at the surface layer at a speed of 0.5 m/s. The results have obtained 71 species belonging to 11 groups, of which 62 species are fish food. The average abundance in the whole sea is 14,844 individuals/m3. Copepoda is the most diverse species composition (46 species) and also dominates in abundance. In the rainy season, the indicators of species composition, abundance, diversity index (H') and diversity value of community (Dv) are higher than those in the dry season. This may reflect that the ecological conditions between the two seasons in Kien Giang sea are diffirent. So in mariculture, it is necessary to pay attention to the change in ecological conditions from the seasonal change. In addition, in the rainy season, a group of freshwater zooplankton has been recorded in the Duong Dong sea of Phu Quoc island, which is also a point to note for mariculture in this place.