The invention belongs to the technical field of lithium-ion battery materials and particularly relates to a preparation method of a nickel-cobalt-manganese ternary positive material precursor of a lithium-ion battery. The preparation method comprises the following steps that: three metal ions of nickel, cobalt and manganese are respectively precipitated in different reaction kettles, but the reaction time is very short, the precipitation particles cannot become large, then microprecipitation particles such as Ni(OH)2, Co(OH)2, Mn(OH)2 or NiCO3, CoCO3 and MnCO3 are formed, and then the microprecipitation particles are mixed together and fully react to form the ternary precursor particles. The preparation method has the advantages that the growth environments of primary precipitated particles and secondary precipitated particles are respectively controlled, so that the crystallization process of precursor particles is more optimized; by comparison with the traditional coprecipitation method, the degree of crystallization of the precursor is obviously higher than that of the traditional coprecipitation method, so that the material synthesized by the precursor has a more excellent electrochemical property than the material synthesized by the traditional coprecipitation method.