The invention relates to a chemical purification method, and in particular relates to a preparation method of amorphous nickel sulfide. The preparation method provided by the invention is obviously different from the traditional nickel sulfide preparation method and is characterized in that a stabilizer is added when sodium sulfide is dissolved, so that the oxidation of the sodium sulfide is avoided and the system reducibility is ensured at the same time; a dispersant is added, so that a polysulfide is prevented from formed in the sodium sulfide; and a reducing agent is added into a copper suspension, so that the reducibility of the system for preparing the nickel sulfide is presented. When the amorphous nickel sulfide is prepared, the adding quantity of the sodium sulfide is controlled and the even stirring is carried out, so that the local excess sulfur source is avoided, namely, the polysulfide formed due to the local excess sulfur source is avoided; and meanwhile, the dispersant is added, so that the collision probability among the nickel sulfides is reduced, namely, the activity of nickel sulfide is maintained for a long time. According to the traditional method, after the prepared nickel sulfide is placed in the air for 24 hours, the copper removal activity of the nickel sulfide is gradually decreased; and after the prepared nickel sulfide is placed in the air for 48 hours, the copper removal activity of the nickel sulfide is decreased to 15% to 20%. According to the method provided by the invention, after the amorphous nickel sulfide is placed in the air for 7 days, the copper removal activity of the amorphous nickel sulfide can be still maintained at 80% to 90%.