A floating production, storage and offloading(FPSO) unit is a facility for developing oil and gas found under the ocean for the processing of hydrocarbons and for storage of oil. The separators are FPSO topside facilities designed to separate a measure water, gas and oil rate. This paper will explore the possibilities of utilising CFD techniques on the three-phase separator design with FPSO motion. The influence of baffle and weir arrangement has been studied with CFD simulations including motion mitigation. The research would show the flow patterns inside the three phase separator for the typical shaped of baffle by using CFD analysis.