The invention discloses a positive electrode active material of a lithium-ion secondary battery, which structurally comprises three layers, the three layers are respectively a matrix positioned on a center, a co-crystallizing grid layer covering the matrix and a covering layer covering the co-crystallizing grid layer, wherein the matrix is made from metallic oxide containing lithium, the co-crystallizing grid layer is made of the matrix material mixed with transition metal, and the material of the covering layer is metal oxide ZOi, phosphate Z (PO4)j or fluoride ZFk. Compared with prior art, the positive electrode active material of the lithium-ion secondary battery adopts a three-layer structural material in design, the covering layer on the outermost layer is made of stable ceramic material, the direct effect of electrolyte and active material can be effectively improved, the co-crystallizing grid layer and the matrix material are in eutectic cladding, so as to enable the transportation of Li+ to be free from blockage. Therefore, the purpose of expanding positive electrode active material charging to end voltage is achieved.