Efficiency and compactness are core strengths of the supercritical carbon dioxide (sCO2) Brayton cycle, which is considered an alternative to the steam Rankine cycle for moderate-temperature heat sources (350−800 °C). Numerical investigations on system design and analysis have received considerable attention, with the aim of improving the sCO2 cycle from the viewpoint of thermodynamics. This paper reviews and compares previous studies in the literature to survey different cycle layouts, operating parameters, and working fluids of the sCO2 cycle. Performance enhancement approaches are categorized into three classes according to characteristics: conventional methods, CO2 mixtures, and combined cycles. The strengths, weaknesses, and limitations of each categorized method are discussed. This research is expected to provide a roadmap for performance improvement that meets the interests of researchers.