The electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA), an important platform chemical for renewable polymer industry, is receiving increasing interest. In this study, nickel borides (NiBx) doped with different amounts of phosphorus were prepared by a simple method and applied to the electrocatalytic oxidation of HMF. It was found that the FDCA yield on P-doped NiBx (NiBx-P-y) gradually improved first and then decreased with the increase of phosphorus content. When NiBx-P-0.(07) (n(p)/n(NI) = 0.07) is used as the electrocatalyst, the FDCA yield reached the maximum (90.6%) and Faradaic efficiency was 92.5% at the potential of 1.464 V (vs RHE). XPS results indicate that the P dopant made relative displacement of electrons from surface nickel happen and surface nickel hydroxide species increased, which has a beneficial effect on its electrocatalytic performance. Furthermore, appropriate phosphorus doping accelerated charge transmission capability of NiBx-P-y, and then improved its activity. NiBx-P-0.(07) also has good stability in the potentiostatic electrolysis of HMF.