The invention discloses a method for producing a Ni-Co-Mn ternary hydroxide, and relates to a continuous synthesis method for a Ni-Co-Mn ternary hydroxide for a lithium ion battery. The method is characterized by comprising the following steps in a production process: first, adding a sodium hydroxide solution and an ammonia water solution into a Ni-Co-Mn metal salt solution, controlling the pH value of a reaction system to be 10.0-12.0, and carrying out a crystal nucleus creating reaction till the granularity of a created crystal nucleus reaches 3-5 [mu]m, so as to obtain a mixed solution containing the crystal nucleus; then, converging the mixed solution containing the crystal nucleus, the Ni-Co-Mn metal salt solution, the sodium hydroxide solution and the ammonia water solution, controlling the pH value of a system to be 9.5-11.5, carrying out a crystal nucleus growth reaction, and carrying out aging, filtration, washing and drying to obtain the Ni-Co-Mn ternary hydroxide. The Ni-Co-Mn ternary hydroxide produced according to the method is stable in product performance, narrow in granularity distribution, less in micro powder, and controllable in morphology.