The invention provides a preparation method of an 
alumina composite 
nickel-
cobalt lithium manganate ternary material. The preparation method comprises the following steps: (1), preparing liquor A; (2), preparing liquor B; (3), installing and configuring a reaction flask; (4), adding the liquor A and the liquor B into the reaction flask to participate in 
hybrid reaction; (5), preparing liquor C, and adding into the flask for reaction; (6), obtaining a precursor by suction-filtering, washing and 
drying; and (7), mixing and 
roasting the precursor with a 
lithium source to prepare the 
alumina composite 
nickel-
cobalt lithium manganate ternary material. The preparation method disclosed by the invention has the beneficial effects that firstly, liquid-phase 
coating is adopted, production preparation period is short, efficiency is high, and 
coating and dispersing are uniform; secondly, the 
coating layer 
alumina on the surface of the ternary material is a film with an amorphous structure, so that charging and discharging 
voltage difference is reduced, multiplying 
power performance and high-performance performance of the material are improved; and thirdly, characteristics of a 
solid-
liquid phase interface among an 
anode material, 
electrolyte and a diaphragm are improved by alumina film-coating, so that velocity and efficiency of electrochemical reaction are improved.