Abstract: The embrittlement of the cladding materials and the fuel swelling caused by Ln fission products are the main problems in the service of UZr metal fuel. The quick diffusion is usually by means of fission gas release channels, and it is observed in experiments that the Ln fission products will segregate to the fission gas bubbles and bubble connection zone in UZr metal fuel. In order to understand the diffusion mechanism of fission products and the phenomenon of surface segregation, in this work, first-principle calculations were carried out to investigate the atomic structure and formation energy of (100), (112), (001), (021), (110) and (010) free surfaces in low-temperature α-U, and the segregation behavior of fission products La, Ce, Pr and Nd on different free surfaces. The results show that the formation energy of (110) free surface is the lowest, 1.75 J/m², followed by (112), (021) and (001) free surfaces, 1.81-1.83 J/m², and the formation energy of (010) and (100) free surfaces are 1.96 and 2.04 J/m², respectively. Ln fission products all tend to segregate to the free surfaces, and the segregation strength of the four Ln fission products is in the order of La>Ce>Pr>Nd. The segregation energy decreases with the increase of the interlayer spacing for six free surfaces. Furthermore, using the Mc-Lean equation, the occupation of the fission products on the surfaces of α-U was estimated thermodynamically, and the results suggest that within the service temperature range, the four Ln fission products all segregate to the surfaces.