The invention discloses a nitrogen-doped carbon-clad manganese oxide lithium ion battery composite cathode material, and a preparation method and an application of the composite cathode material. The composite material is composited by nanoscale manganese oxide and dopamine, wherein manganese oxide is spherical. The method comprises the steps of mixing a prepared spherical manganese oxide nano particle and dopamine hydrochloride, performing filtering, washing and drying to obtain a manganese oxide and polydopamine composite, and then converting a polymerization layer into a nitrogen-doped carbon layer by high-temperature carbonization. The prepared nitrogen-doped carbon-clad manganese oxide (MnO@NC) lithium ion battery composite cathode material is stable in structure and good in conductivity, and has excellent rate capability and cycling stability as a lithium ion battery cathode material; and polymerization of the dopamine is only completed at a room temperature and under a slightly alkaline condition, so that the composite cathode material is low in cost, low in energy consumption, convenient to control and environment-friendly, is suitable for a practical application of a lithium ion battery, and can realize industrial mass production.