The invention discloses a preparation method of electronic copper foil, which comprises the following step: by adding an organic additive group, which is composed of gelatin collagen, cellulose, sodium 3-mercapto-1-propanesulfonate and thiazolidine thione, during raw foil manufacturing under the current density of 7000-8000 A/m<2> and using an additive mixture, which is composed of hydrochloric acid, sodium wolframate, polyethyleneglycol and 2-mercaptobenzimidazole, in the coarsened layer treatment process, carrying out coarsening, coarsening, solidifying, solidifying and solidifying on the coarsened layer to prepare the ultralow-contour high-temperature high-elongation-percentage electronic copper foil. The electronic copper foil prepared by the method has ultralow contour, the rough surface roughness Rz is less than or equal to 3.8 mu m, and the high-temperature elongation percentage is greater than or equal to 15%; uniform compact fine copper teeth are formed on the copper foil rough surface, so the peel strength is high, and thus, the peel strength of the copper foil for FR-4 boards can reach 1.2 N/mm; the copper powder generated in the circuit board manufacturing process is reduced; and the risk for short circuit in the fine circuit board manufacturing process is lowered.