The invention provides a novel nano-carbon-fiber heating floor and a preparation method thereof. The preparation method comprises the following steps: (1) placing nano polyacrylonitrile fibers prepared by electrostatic spinning in a roasting oven, performing heat treatment by using air as a medium, and performing carbonization treatment under nitrogen environment so as to obtain carbonized nano polyacrylonitrile fibers; (2) stirring plant protoplasm fibers and a cationic surface active agent under a closed condition and normal temperature till a uniform mixture is obtained, adding the carbonized nano polyacrylonitrile fibers and nano graphite powder in the mixture, stirring the carbonized nano polyacrylonitrile fibers, the nano graphite powder and the mixture at a high speed, and preparing sheet type flexible macromolecule materials by a hot-pressing technology; (3) fixing metal-sheet electrodes at both ends of the sheet type flexible macromolecule materials by a silver solution so as to form a conductive heating layer; and (4) shearing a solid-wood layer, an insulation layer, the conductive heating layer, a temperature control layer, another solid-wood layer and a surface treatment layer with appropriate sizes from bottom to top, and performing combination so as to form the nano-carbon-fiber heating floor.