ETRI has been developing the Ku and Ka band communications satellite payload system to provide the multimedia services, such as satellite Internet, DTH (Direct to Home), VOD (Video on Demand), and so on. ETRI in cooperation with domestic companies are under design phase for the payload system development. At a conceptual design phase, ETRI studies service requirement and system performance specifications. After analyzing system parameters, we confirm that system performance satisfies system requirement specification. This paper focuses on the conceptual design analysis to verify the system performance specification, especially EIRP, G/T, SFD, etc.