The invention discloses a preparation method of a micropore copper foil used for a negative electrode current collector of a lithium ion battery, and belongs to the technical field of an apparatus fordirectly converting chemical energy into electric energy. The preparation method comprises the steps of (1) processing a titanium alloy roller; (2) preparing a second working solution, comprising 40-70 parts of copper sulfate, 90-100 parts of sulfuric acid, 80-100 parts of polyethylene glycol, 20-30 parts of sodium bromide and 1,000 parts of water based on parts by mass; and (3) preparing the micropore copper foil. According to the method, the processed titanium alloy roller is adopted, so that corrosion resistance is improved and the purity of the copper foil is improved, thereby maintaininghigh conductivity of copper; in addition, the surface evenness of the titanium alloy roller is also improved, and distribution uniformity and dimensional uniformity of hydrogen bubbles on the rollerwall are also facilitated, so that micro pores with uniform hole diameters are prepared; and by virtue of a synergistic effect of bromide ions and polyethylene glycol additive in the second working liquid, the hole diameters can be more uniform, the hole wall quality can be higher, the porosity is lowered, and the conductive performance and mechanical performance of the micropore copper foil are improved.