The invention relates to a method for preparing an electrochemical nano dot array electrode by using an ultra-long nanowire, and belongs to the technical field of nano electrode preparation. In orderto simply, efficiently and repeatedly prepare a nano dot array electrode, the method includes: pouring PDMS on a silicon template containing a micron groove array; pouring resin on the cured PDMS moldto obtain a resin block with a micron groove array; and depositing a layer of metal film on the resin block, performing embedding with resin, carrying out nano slicing, transferring a single resin sheet containing the nanowire array or a plurality of resin sheets containing the nanowire array alternately stacked with the hollow resin sheets to the substrate, lapping and fixing the lead on the surface of the nanowire array, adding resin for packaging, and trimming and polishing one end of the non-lapped wire to obtain the nano-dot array electrode. According to the invention, the overlapping ofthe capacitance and the diffusion layer of the adjacent electrode is avoided, and the new clean nano dot array can be obtained by re-trimming and polishing the end surface of the nanowire, so that the long-term repeated use of the nano dot array electrode is facilitated.