The invention discloses a novel gradient-doped cathode material and a preparation method thereof. The material is Ni gradient-doped lithium cobaltate particles. The preparation method of the novel gradient-doped cathode material includes the steps that a nickel salt solution is gradually added into a cobalt salt solution at a certain flow rate, and meanwhile the nickel-cobalt mixed solution and alkaline liquor converge to be added into a reaction still for reactions. Precipitates are separated, washed, dried and then mixed with a lithium source, and final products are obtained after high-temperature treatment is completed. The preparation method is simple in process, the operation process is controllable, the Ni gradient-doped lithium cobaltate material can be obtained through one-time sintering, and the prepared lithium cobaltate material has higher structural stability, higher discharge capacity and excellent circulation performance under high voltages.