The invention relates to a making method of a NiO nano-crystalline electrochromic film, and belongs to the technical field of functional materials. The method comprises the following steps: preparing NiO nano-crystals through an injection technology, adding a proper amount of n-hexane, carrying out ultrasonic dispersion, and fully stirring to obtain stable ink; and making the NiO nano-crystalline electrochromic film through a Czochralski technology. The ink prepared in the invention is stable, can be used in large-area production of the NiO electrochromic film, provides a new idea for development of green and environmentally-friendly low-cost and high-chromic performance NiO electrochromic film technology, and can promote industrial rapid development of NiO electrochromic film materials and intelligent windows.