Abstract: The million-kilowatt sodium-cooled fast reactor is a mature and commercially promising reactor type, playing a key role in the integrated closed sodium-cooled fast reactor nuclear energy system (integrated fast reactor). Currently, in China, there is no such million-kilowatt sodium-cooled fast reactor unit because of some special factors. The China Experimental Fast Reactor (CEFR) has formed the basis for sodium-cooled fast reactors in China. The million-kilowatt sodium-cooled fast reactor represents an optimization and improvement of the CEFR, sharing the same heat-transfer mechanism. This study used the heat-transfer model validated by CEFR, and set up the reactor core heat transfer model, heat exchange equipment heat transfer model, thermoelectric conversion model, and ultimate heat sink model for the million-kilowatt sodium-cooled fast. The model was validated using two sets of actual operational data from the CEFR at 40% rated power and 100% rated power, and the relative error of electric power was found to be less than 1.3%. The reactor core heat transfer model was validated by substituting the core data from the French million-kilowatt sodium-cooled fast reactor (Super Phenix) into the model and comparing the results with the calculated values. The discrepancy between the reactor core flow rate and the actual flow rate is found to be within 2%. These data all confirm the correctness of the model. This paper conducted a thermal parameter research analysis on the million-kilowatt sodium-cooled fast reactor by referencing the process system parameters of overseas large-scale sodium-cooled fast reactors, such as Russian BN-600 and BN-800, and France Phenix and Super Phenix. By integrating relevant international research findings, the study aims to explore and analyze the thermal-hydraulic characteristics of the sodium-cooled fast reactor at the megawatt level, thereby providing theoretical support and practical guidance for the development of sodium-cooled fast reactor technology in China. Under the premise of ensuring reactor safety, with a focus on the safety and reliability of the core, the feasibility of the system, the characteristics of the coolant and materials, the level of equipment manufacturing, and the appropriate reduction of manufacturing costs while lowering thermal efficiency, the thermal-hydraulic parameters of the million-kilowatt sodium-cooled fast reactor were analyzed. Finally, the system pressures for each circuit were determined, and matching of the primary thermal-hydraulic parameters for the primary, secondary, and third circuits was conducted. The calculation results show that, excluding the electricity consumed by the power plant’s own operations, the electrical efficiency of the power plant is at least 42.72%. The thermal parameters determined in this paper are more economical, effective, safe, and feasible. They can offer references for the development of million-kilowatt sodium-cooled fast reactors in China, boost the competitiveness of nuclear energy in the power field, accelerate the development of China’s integrated fast reactor, and safeguard its rapid growth.