The invention relates to a preparation method for an MoP@C nanowire which is formed by the lapping joint of MoP@C nano-particles and is coated with carbon. The MoP@C nanowire is formed by the lappingjoint of MoP@C nano-particles, wherein the length of the nanowire is 2-4 microns, and the diameter is 100-200 nanometers. The nanowire has abundant hole structures, the main hold diameters of the holestructures are within the range of 15-20 nanometers, the BET specific area can reach 26m2/g, and the thickness of the coating carbon layer is 2-5 nanometers. The beneficial effects of the invention are that the nanowire is based on a nano-structure optimization mechanism; the nanowire which is formed by the lapping joint of MoP@C nano-particles and is coated with carbon is synthesized through a simple and convenient method. When the nanowire which is formed by the lapping joint of MoP@C nano-particles and is coated with carbon is taken as a negative electrode material of a sodion capacitor, the nanowire is excellent in multiplying power and circulating stability. Moreover, a full capacitor formed by the assembly of the nanowire and Na3V2O2(PO4)2F presents excellent electrochemical performances.