Copper nanowires (CuNWs) are becoming an indispensable item for next-generation transparent optical devices due to their excellent conductivity and transparency. In this work, ultrathin semicircle-shaped copper nanowires(SCuNWs) with a diameter of ~ 15 nm and a length of ~ 30 μm (aspect ratio of ~2, 000) were synthesized in ethanol solution. The mechanism and factors that affect the morphology and dispersity of the SCuNWs were investigated. The prepared SCuNWs were coated on polyethylene terephthalate (PET) or polydimethylsiloxane (PDMS) substrate to fabricate flexible transparent conductors (FTCs). The fabricated FTCs exhibited excellent optoelectrical performance and low haze. In addition, the fabricated FTCs showed high mechanical stability during stretching and bending, indicating their great potential in flexible optical devices.