The present disclosure discloses a high-performance lithium-nickel-manganese-cobalt oxide (LNMCO) cathode material for power batteries and a preparation method thereof, and belongs to the technical field of lithium-ion battery (LIB) materials. The preparation method of an LNMCO cathode material of the present disclosure combines a melting and mixing method, a spray drying method, a sol-gel method, and a high-temperature solid-phase method to achieve thorough mixing of various components of a precursor, such that a prepared product has a uniform particle size, excellent electrochemical performance, and high cycling stability. The method has simple operation steps, low raw material cost, small time consumption, and high production efficiency, and can realize industrialized large-scale production. The present disclosure also provides an LNMCO cathode material prepared by the method, which has high specific charge/discharge capacity, thermal stability, and cycling stability.