Abstract: The main problem in today mangrove crab hatchery is the low survival rate of larvae at the zoea and megalopa stages in entering the crablet stage caused by a less than optimum rearing environment. This study was aimed to determine the optimum salinity that produces the best survival rate and growth rate of mud crabs (S. olivacea) at the megalopa-crablet stage. Research The research was carried out at the Center for Brackish Water Aquaculture Development (CBAD), Bonddia Village, Galesong District, Takalar Regency, South Sulawesi, Indonesia. The test animals used were mangrove crabs at the megalopa stage which were stocked at a density of 5 individuals/L and reared until they entered megalopa. The research used a container in the form of a black plastic basin with a volume of 30 L filled with 12 pieces of 20 L of water.