The HeCEL-3 is a high temperature, high pressure and high flow-rate helium cooling experimental loop (HeCEL), mainly used for thermal-hydraulics experiments of blanket components of fusion reactor. According to the system design and layout parameters of the experimental loop, the loop was modeled using APROS software to simulate the distribution and variation of important process parameters such as temperature, pressure and flow-rate of helium under different working conditions. The simulation also includes the transient parameters of critical equipment, such as printed circuit heat exchanger (PCHE) and circulator, during operation or state transitions to generate the thermal characteristics curve. Currently, the HeCEL-3 has been constructed, and preliminary experimental studies on some operational states of the loop have been conducted. The thermal characteristics obtained from simulation are compared with the experimental parameters to verify the effectiveness and applicability of the APROS simulation method, providing references for the future design and operation of helium cooling loops for fusion reactors by means of this method.