In order to improve the low-frequency vibration isolation performance of the floating raft isolation system, the design method of arranging locally resonant cells on the surface of the raft frame periodically is proposed, and the dynamics model of the locally resonant floating raft isolation system is constructed, and the influence of the resonant cells on the low-frequency vibration isolation performance of the floating raft isolation system under single-frequency and multi-frequency vibration excitation is analyzed with the output power flow of the system as the evaluation index. Results shows: the output power flow of the system can be reduced by about 30% when the mass of the additional resonators is less than 10% of the raft mass; the output power flow of the system at multiple frequencies can be reduced simultaneously when the resonant cell contains resonators of different natural frequencies. The research results can provide theoretical guidance for improving the low-frequency vibration isolation performance of the floating raft isolation system by using locally resonant structure.