The disclosure discloses a nickel cobalt manganese hydroxide, a cathode material, a preparation method thereof and a lithium ion battery. The nickel cobalt manganese hydroxide comprises a core and an outer layer covering the outside of the core. The core comprises flaky particles, the D50 particle diameter of the flaky particles in the core is 5-8 μm, and the D50 particle diameter of particles in the outer layer is 0.1-5 μm.