The invention discloses a method for preparing ornithine aspartate powder injection for injection. The method comprises the following steps of: taking arginine, adding the solution of barium hydroxide, stirring to dissolve the arginine, and heating to hydrolyze so as to completely transform the arginine into ornithine; adding aspartate, uniformly stirring, adding a precipitator, filtering to remove barium ion precipitate, and regulating the pH value of the solution to neutrality; adding an inert organic solvent for crystallization, filtering and pumping, adding water for injection to dissolve the crystals, adding active carbon for needle for decoloration and depyrogenation, coarsely filtering to remove carbon, and filtering to make the solution sterile and clarified by using a 0.22 mu m millipore filter; and adding ethanol for crystallization, obtaining ornithine aspartate sterile powder, packaging the powder into a sterilized vial, capping, and rolling an aluminum cover to obtain the ornithine aspartate sterile powder injection for injection. The method has the advantages of increasing the yield, preparing the ornithine aspartate by the one-pot method, along with easy operation, simple and convenient operation, low cost, short production period, and suitability for mass production.