The invention relates to a lithium silicate-coated Ni-Co lithium aluminate positive electrode material and a preparation method thereof. The mass percent of lithium silicate in the material accounts for 1-10wt%, a coating layer with a thickness being 2-20 nanometers is formed from the silicon silicate and is coated on Ni-Co lithium aluminate, and the positive electrode material is a spherical particle with a grain size being 5-15 micrometers. The method comprises the following steps of (1) adding a silicon source into an organic solvent, performing uniform stirring, adding water, adding Co-Alnickel hydroxide, performing heating and stirring reaction, and performing drying to obtain silicon dioxide-coated Co-Al nickel hydroxide precursor powder; and (2) grinding and uniformly mixing the silicon dioxide-coated Co-Al nickel hydroxide precursor powder and a lithium salt, placing the mixture in a tubular furnace, and performing two-segment calcination under an oxidization atmosphere, thereby obtaining the lithium silicate-coated Ni-Co lithium aluminate positive electrode material. The positive electrode has relatively good cycle stability and large-rate discharging performance; and bythe method, the problem of lithium resided on a surface during conventional coating can be effectively reduced, and the method is low in cost and simple in process and is suitable for industrial production.