Multifunctional bio-based nano-ZnO/PA56 composite fibers were prepared by loading nano-ZnO with bio-based PA56 as the matrix and using melt spinning technology. The morphological structure, thermal and crystalline properties of the fibers were characterized by SEM, FTIR and XRD, and the mechanical, thermal conductivity, and UV aging resistance properties were investigated. The results showed that nano-ZnO was uniformly dispersed in the matrix, and the addition of nano-ZnO decreased the mechanical properties and thermal stability of the composite fibers and increased the crystallization temperature of the composite fibers, indicating that nano-ZnO nucleated heterogeneously in the composite fibers, and the mechanical properties of the composite fibers were reduced from 3.47 cN dtex-1 to 3.06 cN dtex-1, which showed good mechanical properties. The composite fiber has excellent antibacterial, thermal conductivity and UV aging resistance, and the composite fiber with 0.5 wt% nano-ZnO content has 100% inhibition of E. coli and S. aureus, and the surface temperature of the fiber is increased by 16 oC in 50 s. The mechanical properties of the 2.0% nano-ZnO/PA56 composite fiber are 9.9% lower than that of the PA56 after 140 h of UV aging. fiber degradation rate was 9.9% lower.