Lyotropic liquid crystals (LLCs) are thermodynamically stable solutions that exhibit orientational order and sometimes partial positional order. In this study, by utilizing the LLC mesophase, we demonstrated that carbon nanotubes (CNTs) with different lengths can be effectively sorted. At the isotropic cloud point, long CNTs formed nematic domains, whereas short CNTs remained in the isotropic phase. This enabled selective length sorting driven by differences in surfactant adsorption probability. The sorted CNTs were then purified by heat treatment and dialysis to remove amorphous carbon and residual surfactant species. The resulting CNT fibers had a tensile strength of 1.76 GPa and an electrical conductivity of 4.17 MS/m, surpassing those of fibers produced from unsorted CNTs. This research was supported by the Korea Institute of Science and Technology institutional program (26E0352), and the Ministry of Trade, Industry & Energy (MOTIE RS-2023-00258591)