Abstract: In the technical field of lithium ion batteries, disclosed is a wet synthesis method of a high-nickel NCMA quaternary precursor. The method includes synthesizing solid tiny crystal nuclei of the NCMA quaternary precursor in a first reactor, and prompting the crystal nuclei of the quaternary precursor to grow to a certain particle size in a second reactor, wherein in the first reactor, an upper feeding mode is used to continuously produce the solid tiny crystal nuclei of the NCMA quaternary precursor. In the second reactor, an upper-and-lower dual feeding mode is used to prompt the continuous growth of the solid tiny crystal nuclei of the NCMA quaternary precursor. During a washing process, the NCMA quaternary precursor is washed with a mixed alkali solution of sodium carbonate and sodium hydroxide at certain concentration, so that Na can be reduced below 50 ppm and sulfur can be reduced below 800 ppm.