Abstract: The present disclosure discloses a cathode composite material for a lithium-ion battery (LIB), and a preparation method thereof. The cathode composite material for an LIB is composed of a lithium-containing matrix and a three-layer coating layer coated on a surface of the matrix, where the three-layer coating layer includes a lithium-deficient matrix material layer, a lithium-deficient lithium cobalt phosphate (LCP) layer, and a cobalt phosphate layer in sequence from inside to outside. The cathode composite material of the present disclosure can reduce the oxidation of a highly-delithiated cathode material to an electrolyte under high voltage, and has a high energy density.