The invention discloses a preparation method for a porous sodium vanadium pyrophosphate positive electrode material of a sodium-ion battery. According to the method, nitrogen-doped carbon-coated porous sodium vanadium pyrophosphate particles with uniform particle sizes are prepared by using a hydrothermal method. The preparation method comprises the following steps: subjecting vanadium-source monomers and nitrogen-containing carbon-source monomers to a hydro-thermal reaction so as to allow a corresponding conductive polymer to grow on vanadium oxide particles in situ; subjecting a hydro-thermal product, a sodium source and a phosphorus source to ball milling so as to obtain a precursor; and successively carrying out calcining, washing and drying so as to obtain the nitrogen-doped carbon-coated porous sodium vanadium pyrophosphate particles with uniform particle sizes. Moreover, the invention also discloses the positive electrode material of the sodium-ion battery prepared by using the preparation method. The preparation method provided by the invention is simple in process and low in cost for raw materials. The prepared material is nitrogen-doped carbon-coated porous sodium vanadium pyrophosphate. The hydrothermal method is employed for in-situ generation of the conductive polymer on the surface of the vanadium source to adjust the morphology of the material and uniformity of a carbon layer; and the material is used for the sodium-ion battery and shows excellent electrochemical performance.