With the development of offshore oil and gas exploitation intensifies, FPSO which having many advantages can better adapt to the complicated environment of deep sea in numerous offshore platform. Due to the hull prone to resonance phenomenon, FPSO has more intense motion compared to other platforms. Therefore, the main challenge of FPSO in the deep sea operation is to design effective mooring system. This paper introduced the dynamic response analysis methods of FPSO system. Time domain method of coupling analysis was used. Dynamic responses of catenary and taut inner tower FPSO system were calculated respectively. According to the current mooring system development, the article compared and analyzed catenary mooring system and taut mooring system. Moreover, the results indicated that the position ability and mooring strength of taut mooring system whose intermediate material is polyester are better than that of catenary mooring system on the premise that satisfies API specification at the same time.