The invention discloses a fast design analysis method suitable for a vibration reducing and isolating system of a large reciprocating type compressor unit of an ocean platform. The fast design analysis method includes the following steps that firstly, unbalanced force of a motor and a compressor of the large reciprocating type compressor unit is analyzed, the exciting force frequency of the compressor unit is obtained, and the rigidity characteristic of a vibration isolating device is determined according to the transmission ratio required by the vibration reducing and isolating system; secondly, the structural form of a sledging seat of the large reciprocating type compressor unit and the mass distribution of all main devices of the compressor unit are analyzed, and the arrangement manner of the vibration reducing and isolating device and the design state of the vibration reducing and isolating system of the compressor unit are determined; and thirdly, mode characteristic analysis of the vibration reducing and isolating system of the large reciprocating type compressor unit, harmonic response analysis of the vibration reducing and isolating system and vibration reducing and isolating performance analysis of the vibration reducing and isolating system are carried out in a manner of combining the rigidity characteristic, determined in the first step, of the vibration reducing and isolating device and the arrangement manner, determined in the second step, of the vibration reducing and isolating device, all analysis results are obtained, and the coincidence of the analysis results and design of the vibration reducing and isolating system of the compressor unit is determined.