Around the 1960s, the proposal of the supercritical dioxide (s-CCO2) power-cycle was first introduced; however, because of various obstacles, the development was slow at that time. With current worldwide emission and power problems, the s-CO2 power cycle has regained more attention because of its unique properties as a working fluid for power-cycle, and zero-emission potential. Each s-CO2 power cycle requires various components for compression, expansion, and heat exchange operation. Among various working fluid, s-CO2 has four significant advantages favorable for developers: 1. Relatively low and achievable critical conditions (∼7.3Mpa, ∼31°C). 2. The high density (∼400kg/m3) results in a very compact turbomachinery design. 3. The low dynamic-viscosity of s-CO2 can reduce the overall flow friction loss. 4. Low compressibility value which can reduce the overall system compression works. All these advantages make the s-CO2 the perfect working fluid for next-generation high-efficiency power-cycle design. This paper in two parts reviews the s-CO2 cycle technologies for power generation and critically assesses the recent challenges and development status. This paper, Part I, focuses on the general cycle concepts, thermodynamic properties, materials selection, and other components considerations.