The direct-fired supercritical carbon dioxide power cycle not only has the potential of reaching high efficiency, but also achieves near 100% carbon capture in a more inherent and natural manner. A conceptual flow sheet of the direct-fired supercritical carbon dioxide power cycle that is coupled to the coal gasification process is built in this study. A detailed turbine cooling model is added to better assess the performance of the power plant. To investigate the effect of key cycle variables on the cycle performance and determine potential chances for efficiency improvement, a parametric study is conducted in this paper. The result shows that the turbine inlet temperature and turbine outlet pressure have significant effect on the cycle efficiency while the effect of the turbine inlet pressure is minor. The cycle efficiency is susceptible to the inlet condition of the carbon dioxide pump, which is the weakness of the supercritical carbon dioxide power cycle. The flow sheet and some of the cycle parameters are modified based on the conclusions drawn from the parametric study. The net efficiency of the power plant is calculated to be 38.87% (on lower heating value basis) at a turbine inlet temperature of 1200 degrees C, while capturing most of the carbon dioxide derived from combustion.