The invention relates to a lithium-rich ternary cathode material for a high-capacity lithium ion battery and a preparation method of the lithium-rich ternary cathode material. The method comprises the following steps: charging a prepared precipitating agent and a prepared lithium salt solution into nickel-cobalt-manganese metal salt solution dissolved with organic macromolecular substances, thus preparing slurry containing nickel, cobalt, manganese and lithium, stirring, standing for a period of time, spray drying the slurry to obtain precursor powder, and then roasting the precursor powder at high temperature to obtain high-capacity cathode material Li<1+x>NiyCozMn<1-y-z>O2, wherein x is more than 0.2 and less than 0.5, y is more than zero and less than 0.5, and z is more than zero and less than 0.5. The prepared cathode material is high in capacity, good in circulating stability, simple in preparation process, easily available in raw materials and easy in realizing industrialized production.