The invention discloses an in-situ conducting polymer coated Ni-Co lithium aluminate cathode material and a preparation method thereof. The chemical formula of the cathode material is Lib(NixCoyAlzRa)O2@e-polymer, wherein (x+y+z+a):b = 1:(0.9 to 1.1), (x+y+z):a = 1: (0.01 to 0.05), x > 0.33, R is at least one of rare earth elements, and e-polymer is a conductive polymer having electrochemical activity. Thus, by doping the Ni-Co lithium aluminate cathode material with rare earth ions, the structural stability of the material is improved. The conducting polymer coated Ni-Co lithium aluminate cathode material is isolated from an electrolyte to avoid direct contact between the Ni-Co lithium aluminate cathode material and the electrolyte and reduce side reactions. Further, the electron and ionconduction of the material can be improved, thereby improving the rate performance of the Ni-Co lithium aluminate cathode material.