Abstract: The computational fluid dynamic simulation on the heat transfer characteristics during depressurization transient under supercritical pressure was performed in this paper by adopting Ansys Fluent 15.0 software based on available experimental data. The reliability of the calculation was verified by comparing the computational results with the experimental data, and the simulation method established in this paper was practical and applicable for transient heat transfer during depressurization under supercritical pressure. The calculation results indicated that the parameters at the outlet of the test section exceeded the pseudo-critical point but still stayed in the area where the thermal physical properties varied dramatically in simulated transient condition with thermal parameters nearby the critical point. The incompressible flow at the inlet of the test section was turned to compressible flow at outlet region. Furthermore, there was a phenomenon of peak around pseudo-critical point for both mass flow flux and pressure gradient. In addition, the classical steady-state supercritical heat transfer correlation–Jackson empirical correlation overestimated the Nusselt number obtained in the computation by about 20%~50% near the critical point region.