Abstract: The HE-FUS3 facility was organized to assess the capability of system code in simulating the thermal-hydraulic and dynamic behavior for High Temperature Gas Reactor. The TSACO（Thermal hydraulic and Safety Analysis code） modeled the HE-FUS3 helium facility at the initial steady state and loss of flow accident（LOFA）. The calculated temperature distributions in the loop at the initial steady state are compared with the measured temperatures. The flowrate and test section outlet temperature for LOFA are compared. The calculated results at both steady state and LOFA accident are in good consistent with the experimental results. Good agreements of the experimental and computational results proved the rationality and accuracy of the TSACO modeling.