In transcritical CO2 refrigeration systems, replacing the throttle valve with a two-phase ejector markedly enhances energy recovery during the expansion process. This study comprehensively reviews the application of supersonic flow visualization techniques in two-phase ejectors. The first section elucidates the internal flow states of the two-phase ejector and summarizes key indicators of interest in visualization experiments. The second section details various visualization methods applied to two-phase ejectors and synthesizes the main findings from previous experiments. The third section critically evaluates the advantages and limitations of each visualization approach. Finally, the conclusion outlines insights regarding the future integration of visualization techniques in CO2 refrigeration systems employing two-phase ejectors and emphasizes opportunities for further improvement and innovation.