The primary objective of this study is to improve the accuracy and reliability of space infrared radiation measurements by developing an advanced gallium fixed-point space infrared radiation standard blackbody. By combining the gallium fixed-point with a standard blackbody, stable melting temperature curves during phase transition are reproduced, enabling precise traceability and measurement of in-orbit temperatures. This is crucial for long-term climate monitoring and ensures the traceability of climate data obtained from satellite sources. The project supports the reliable tracking of subtle climate changes over extended periods through satellite observations.The developed gallium fixed point space infrared radiation standard blackbody includes parts such as the inner chamber, outer chamber, protective layer, constant temperature sleeve, shell, grating, and fixed structure. The inner wall is coated with a high emissivity coating, gallium of high purity is poured in, and five temperature sensors and two heating regions are set to precisely control and measure temperature (Fig.1 and Fig.2). The Monte Carlo method for emissivity simulation is a key factor in optimizing the blackbody design, and obtained a theoretical emissivity of 0.9994 through a specific chamber size (diameter of 60 mm, depth of 230 mm, 32° cone angle) as shown in Fig.3. By setting boundary solution conditions and iteratively solving using the finite element method, obtaining the thermal properties such as temperature field uniformity in the phase transition stage of the blackbody (Fig.4). In addition, conducting performance tests such as infrared spectral brightness temperature test, emissivity test, phase transition reproduction test, and radiation-contact temperature comparison.The implemented Gallium Fixed Point Blackbody demonstrated remarkable accuracy and stability in its performance. It achieved a radiant brightness mean temperature of 302.907 K across a wavelength range of 5 μm to 16 μm (Fig.5). The emissivity test result was 0.999 3 as show as Fig.6, slightly lower than the simulated result. Through a four-year phase change repeatability test, it was demonstrated that its long-term repeatability was within 0.003 K (Fig.7). In the radiation-contact temperature calibration comparison, the TRT radiation measurement value exhibited an overall trend consistent with the contact measurement value of the PRT embedded in a blackbody; however, the TRT measured temperature showed an average offset of approximately 25 mK on average. This difference fell within the TRT measurement accuracy. The comprehensive testing results underscored its potential for long-term deployment in space. The close correlation between simulation results and experimental data confirmed the effectiveness of the design in achieving the desired operational reliability and temperature uniformity.This research has successfully developed a Gallium Fixed Point Infrared Standard Blackbody that sets new standards for accuracy and reliability in space-based infrared measurements. According to the evaluation, the standard synthesis uncertainty（k=1） is better than 0.024 K. The blackbody's capability to provide a stable, reproducible reference temperature significantly enhances the calibration accuracy of satellite radiometers. Its proven stability and precision are crucial for future satellite missions focused on climate observation and radiometric calibration, rendering it an indispensable tool in advancing climate monitoring technologies. This breakthrough marks a significant advancement in the field of space radiometry, providing robust support for ongoing and future climate research initiatives.