Abstract: As the largest and non-replaceable key component of a nuclear power plant, the structural reliability of the reactor pressure vessel (RPV) is extremely important throughout its entire service life. It not only concerns whether the reactor can operate safely, but also involves the issue of extending the lifespan of the reactor until later stages of operation. Low Cu materials (≤0.072%) are used for RPV steel to reduce the radiation embrittlement caused by Cu. However, the material performance degradation of the component is still inevitable in the long-term high-energy neutron irradiation environment, mainly manifested as an increase in material brittleness and a decrease in fracture toughness caused by irradiation. The irradiation temperature and the neutron fluence level experienced are the main external variables that cause this degradation process. To analyze the effect of irradiation temperature on RPV steel, this paper summarized 26 neutron irradiation tests conducted in HFETR and MJTR over the past 20 years, analyzed the experimental data and explored the relationship between changes in irradiation temperature and the degree of irradiation embrittlement of RPV steel. The results indicate that irradiation temperature can macroscopically determine the rate of material performance degradation. The experimental data analysis shows that the increase in ductile-to-brittle transition temperature (ΔDBTT) is influenced by both neutron fluence and irradiation temperature. At a constant neutron fluence level, higher irradiation temperatures reduce the degree of material embrittlement; Whereas at a fixed temperature, higher neutron fluence leads to more severe embrittlement. At an irradiation temperature of 200 ℃ and a neutron fluence level of 9.7×10¹⁸ cm⁻², the ΔDBTT is 98 ℃. At an irradiation temperature of 270 ℃ and a neutron fluence level of 9.6×10¹⁸ cm⁻², the ΔDBTT is 34 ℃. When the irradiation temperature is 240 ℃ and the neutron fluence reaches 2.9×10¹⁹ cm⁻², the ΔDBTT increases to 127 ℃. However, when the irradiation temperature remained at 240 ℃ but the neutron fluence decreased to 1.5×10¹⁹ cm⁻², the ΔDBTT drops to only 49 ℃. Therefore, under the same irradiation temperature conditions, a decrease in neutron fluence leads to a corresponding reduction in ΔDBTT. As irradiation temperature decreases and neutron fluence increases, the ΔDBTT of RPV steel rises more significantly, resulting in a more pronounced irradiation embrittlement effect. When applying the RG1.99-2 model, a temperature coefficient correction is required, but this introduces considerable error and thus it is not recommended for standalone use. The RG1.99-3 model demonstrates high reliability in predicting low-temperature irradiation effects on RPV steels, with predicted irradiation embrittlement values closely matching experimental measurements. Therefore, the RG1.99-3 model is priority recommended. The influence of temperature on ΔDBTT is most significant when the irradiation temperature ranges between 200-240 ℃. When the irradiation temperature exceeds 260 ℃, the impact of temperature on material irradiation response becomes significantly reduced. Within the range of 200-300 ℃, the relationship between ΔDBTT and irradiation temperature for RPV steel follows the typical Arrhenius law.