Single- or multi-component supercritical fluids, which exhibit excellent solubility in polymers, are used as solvents in polymer-based industries. Because their properties change easily with volume, temperature, and pressure, the use of single- or multi-component supercritical fluids in industrial applications requires the supercritical fluid apparatus to be designed according to the required volume, temperature, and pressure. Supercritical fluid apparatus design and optimization can benefit greatly from the analysis and understanding of the thermodynamic behavior of single- or multi-component fluids. Therefore, this study investigated the correlation between the composition ratio of a dichloromethane/ carbon dioxide mixture and pressure at 200 ℃ using ideal gas, van der Waals, Redlich- Kwong, Soave-Redlich-Kwong, and Peng-Robinson equations of state. The critical temperature according to the compositional change of the dichloromethane/carbon dioxide mixture was predicted by the basic mixing rule. This analysis of the thermodynamic behavior of the dichloromethane/carbon dioxide mixture can be used for optimizing supercritical fluid apparatuses.