The invention discloses a ternary composite cathode material with a three-dimensional network structure and a preparation method of the ternary composite cathode material. The preparation method comprises the following steps: (1) mixing an Ni-Co-Mn precursor, a lithium salt and a graphene oxide solution, stirring and dispersing the mixture evenly, adding carbon nano tubes, and further stirring the mixture and the carbon nano tube evenly to obtain a mixed solution; and (2) dewatering the mixed solution, and calcining a solid matter in air atmosphere or inert gas atmosphere at 400-1,000 DEG C for 0.5-24 hours, naturally cooling the solid matter to a room temperature, porphyrizing and sieving the solid matter to obtain the ternary composite cathode material with the three-dimensional network structure. By the characteristic that graphene oxide is easy to disperse, the problem of graphene agglomeration in the prior art is overcome; the three-dimensional network structure is formed by bridging of the carbon nano tubes; and the rate capability of the composite material is improved; and the preparation method disclosed by the invention is simple and feasible in technology process, low in price, beneficial to implementation and very suitable for commercial popularization and application.