Abstract: An investigation on the irradiation temperature and irradiation test of fuel specimens was performed in the High Flux Engineering Test Reactor（HFETR）, for conducting fuel irradiation test in the worst design condition. The test results show that the axial factor of heat flux density on fuel specimen surface can be decreased by adjusting the fuel specimen locations in the irradiation rig with its uranium content. A high irradiation temperature level of fuel meat and fuel cladding in the fuel specimens was obtained by coating the fuel specimens with a layer of liquid lead-bismuth alloy and a stainless steel container, while the specimens were cooled with a rather low temperature coolant of HFETR. The test results show that the stainless steel surface temperature is lower than the limit of maximum cladding surface temperature of the HFETR fuel element under the steady state condition or a short-term transient operation condition, satisfying the requirements of reactor operation and fuel irradiation test. To decrease the peak factor of fuel specimen temperature in the irradiation channel and then to increase its irradiation temperature under the steady state operation condition, the short-term transient power variation of fuel specimens caused by the reactivity disturbance in the irradiation rig should be avoided or reduced by optimizing the core arrangement design and reactor operation plan