Oxy-combustion technologies are green energy systems and an impressive solution to climate change and global warming. This study presents a detailed exergy analysis obtained for oxy-combustion power systems in comparison with a conventional gas turbine power system. The results include net power, overal thermal efficiency, exergy destruction, exergy efficiency, power density, exergetic performance coefficient (EPC), ecological performance coefficient (ECOP), effective ecological power density (EFECPOD), and mean exergy density (MED), and cost of power density (COPD), which are calculated as functions of pressure and oxygen ratios. The conventional gas turbine power system obtained a pressure ratio for maximum net power of 20.8. Similarly, oxy-combustion power cycles at 26%, 28%, and 30% oxygen ratios have respective pressure ratios for maximum net power of 23.3, 27.4, and 29.7. Results from 24%-30% oxygen ratios are displayed to show the reactant oxygen’s effect on the oxy-combustion power cycles. Increases in the pressure ratio show decreases in the total exergy destruction in both the conventional gas turbine power system and the oxy-combustion power systems. Meanwhile, increases in the pressure ratio show increases in the total efficiency, power density, exergy efficiency, EPC, EFFECPOD, and MED in both the conventional gas turbine and the oxy-combustion power systems. In addition, increases in the oxygen ratio in the oxy-combustion power systems show different characteristics for these parameters based on the pressure ratio of the cycle. In terms of COPD, conventional gas turbine power systems are more advantageous than oxy-combustion power systems. Optimum COPD is obtained at a pressure ratio of 25.6.