The Supercritical CO2 (S-CO2) Brayton power cycle has the advantages of relatively high efficiency at moderate heat source temperature compared to a steam Rankine cycle or a helium Brayton cycle and compact components size. In nuclear energy industry, Small Modular Reactors have potentials in many aspects, flexibility of construction, and applicability for the distributed power source and reduced construction cost. Therefore, KAIST research team developed an S-CO2 cooled Small Modular Reactor namely KAIST Micro Modular Reactor (MMR), using both advantages of S-CO2 cycle and SMR. Currently, radial turbine is being used for the output of 12MWe in MMR. The original KAIST-MMR was designed to utilize radial turbine but the 12MWe power output of MMR can adopt axial turbine as well. Therefore, this paper explores the potential of improving both steady state performance and transient response by switching from radial type to axial type turbine. The implications of the transient analysis results show the advantages of using the axial turbine over the radial turbine because the axial turbine operates at relatively higher efficiencies for wider off-design ranges.