Accurate measurement of isobaric specific heat capacity of supercritical fluids is essential for many scientific researches and engineering applications. Based on the flow calorimetry method, an online experiment system for measuring isobaric specific heat capacity for subcritical and supercritical fluids was established. The relative expanded uncertainty of isobaric specific heat capacity was estimated to 2.44%–2.70% (coverage factor k = 2). Based on the verification of the reliability of the measurement system by using pure water, cyclohexane and pentane, the isobaric specific heat capacity of carbon dioxide (CO2) in the temperatures range of (25.0–60.0) °C and pressures range of (6.7–12.0) MPa was measured. The experiment platform can provide accurate data measurement support for further scientific investigations and engineering designs.
