The invention discloses a rich-lithium ternary laminar lithium ion battery cathode material, which has a molecular formula of Li<1+alpha> MnxNiyCozO2, wherein alpha is greater than 0.05 but smaller than 0.5, x is greater than 0.5 but smaller than 0.8, y is greater than 0.05 but smaller than 0.2, z is greater than 0.05 but smaller than 0.2, and the sum of x, y and z is 1. According to a method, a sol-gel method is adopted for preparing the cathode material. The method comprises the following preparation processes that metal salts of soluble manganese sources, nickel sources, cobalt sources and lithium sources are dissolved in water, then, acid complexing agents are added, ammonia water is used for regulating the pH value to be 6 to 8, next, the stirring is carried out at 60 to 90 DEG C, in addition, the water is dried through evaporation, sol-gel precursors are obtained, blocky porous loose precursors are obtained through vacuum drying, then, the ball milling, the pre-sintering, the sintering and the ball milling are carried out, and finally, the cathode material is obtained. The obtained material has the advantages that particles are more uniform and are in the nanometer level, in addition, a battery is assembled for carrying out electrochemical test, and higher capacity and excellent circulation performance are realized.