A process for preparing lithium-nickel-manganese-cobalt composite oxide used as a positive electrode material for the lithium ion battery, comprising subjecting a mixture containing a lithium compound and nickel-manganese-cobalt hydroxide to a first-stage sintering and a second-stage sintering, wherein said process further comprises adding a binder and/or binder solution after the first-stage sintering, and the mixture of the binder and/or binder solution and the product of first-stage sintering is sintered in said second-stage sintering. The tap density and volume specific capacity of the positive electrode material lithium-nickel-manganese-cobalt composite oxide prepared by the present process, come up to 2.4 g/cm3 and 416.4 mAh/cm3, respectively. Besides, the positive electrode material lithium-nickel-manganese-cobalt composite oxide prepared by the present process possesses the advantages of high specific capacity and good cycle stability.