Fuel test loop is a irradiation test facility which can conduct the irradiation tests of nuclear fuels and materials at HANARO. The fuel test loop simulates the operating conditions of commercial nuclear power plant to conduct the irradiation tests. The high temperature performance test of fuel test loop was performed with test fuels in commissioning stage. The reactor was started at the hot stand-by operation mode of fuel test loop and increased the power, and finally reached at full power (30MW). The experimental results show that the performance of high temperature operation such as temperature, pressure and flow satisfy the target operation values.