The invention discloses a preparation method of lithium ion battery positive material nickel cobalt aluminum. The preparation method comprises the following steps: mixing nickel, cobalt and aluminum salt solutions, mixing a precipitator, a complexing agent and the mixed solution of the nickel cobalt aluminum to obtain a mixed solution, adding the mixed solution into a reaction kettle to carry out co-precipitation reaction, adjusting the pH value of the system to 10 to 11 at the temperature of 40 to 60 DEG C, stirring at the speed of 500 to 1500 turns/minute, carrying out reaction for 10 to 30 hours, filtering, washing and drying to obtain a hydroxide precursor; pre-sintering the precursor at high temperature to obtain a nickel cobalt aluminum oxide, mixing the nickel cobalt aluminum oxide with a lithium source to obtain a mixture, sintering the mixture at high temperature under an oxygen atmosphere, and crushing and sieving to obtain the nickel cobalt aluminum powder. By calculating the pre-sintering loss rate of the precursor, the content of Ni<2+> and the content of Ni<3+> in the nickel cobalt aluminum oxide at different temperatures are analyzed by utilizing XPS, so that the nickel cobalt aluminum oxide with the highest content of Ni<3+> can be obtained, more nickel ions in the secondary sintering process can be promoted to be converted into Ni<3+>, the mixed arrangement of the Li<+> and the Ni<2+> can be reduced, and the electrochemical performance of the material can be improved.