The invention discloses a preparation method of a ternary positive electrode material of a high-nickel monocrystal-like lithium ion battery and the prepared ternary positive electrode material. The preparation method comprises the following steps: sintering a precursor and a lithium source in air or oxygen; uniformly mixing the precursor metal oxide A and lithium oxide obtained by sintering according to a molar ratio of lithium to metal ions in A of 1.0-1.1, and carrying out primary sintering in oxygen to obtain B; adding 30-70% by mass of B into pure water, uniformly mixing, adding 0.5-3% bymass of an oxidizing agent without metal ions, and stirring at 10-50 DEG C for 10-30 minutes; filtering, drying, carrying out secondary sintering in oxygen, and sieving to obtain the ternary positiveelectrode material LiNi<x>Co<y>Mn<z>M<t>O<2> of the high-nickel single-crystal-like lithium ion battery, wherein x is more than or equal to 0.60 and less than or equal to 0.90, y is more than or equalto 0.05 and less than or equal to 0.20, z is more than or equal to 0 and less than or equal to 0.20, t is more than or equal to 0 and less than or equal to 0.005, x+y+z+t is equal to 1, and M is oneof Al, Ca, Mg, Zr, Ti, Sr, Mo, W and Ce. The ternary positive electrode material of the high-nickel single-crystal-like lithium ion battery contains divalent nickel, has few surface impurities lithiumand impurities, and is good in processability, high in capacity and good in cycle performance when being used for manufacturing the battery.