The SCO2 (supercritical carbon dioxide) Brayton cycle has been recommended to the marine industry due to its high efficiency, small volume and low weight. However, the undulation and sway of ships aroused by the wind and sea waves in the marine environment may generate the periodic changes in multiple forces, and finally leading to the unstable performance of the SCO2 Brayton cycle. Phase change material (PCM) system grabs much attention for its large heat storage capacity and stabilized operation temperature, and has a wide application in the thermal management system, especially for the temperature control of a thermodynamic cycle. In this work, a PCM system is introduced into SCO2 recompression Brayton cycle in order to reduce the response amplitudes of inlet temperatures in main compressor and recompressor. The transient characteristics of cycle parameters affected by the PCM system in a high frequency oscillating environment are studied. The transient analyses indicate that PCM system is able to control the temperature changes and helpful to enhance the stability of cycle performance.