1D ultrathin noble metal nanowires are commonly regarded as high-performance catalysts for fuel cell reactions due to their high-index facets and intrinsic mechanical degradation resistance. However, the controlled syntheses of 1D ultrathin Pt-based nanowires with different lengths and systematic research on the correlation between electrocatalytic performances and lengths of catalysts have been rarely reported. Herein, a robust and large-scale method has been developed for the successful construction of 1D ultrathin Pt₃Co₁ nanowires with the same diameter but different lengths from 11.3 to 58.7, and to 200.0 nm by changing the volume ratios of oleylamine to octadecylene from 4 : 1 to 3 : 2, and 1 : 1. Remarkably, the as-prepared ultrathin Pt₃Co₁ nanowires can display a great enhancement in electrocatalytic activity and durability toward the ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR) in comparison with the Pt/C catalyst. In particular, the optimal Pt₃Co₁ nanowires with the longest length exhibit the highest mass and specific activities of 4905.3 mA mg⁻¹ (9.4 mA cm⁻²) and 3754.6 mA mg⁻¹ (7.2 mA cm⁻²) for the EGOR and GOR, which are 4.4/4.9 and 4.3/4.8 times larger than those of the Pt/C catalyst, respectively. This work may offer guidance for the length-controlled construction of 1D ultrathin Pt-based nanowires with great prospects for application in the electrochemical field.