The invention provides a positive electrode material of a lithium ion battery and a preparation method of the positive electrode material. The lithium ion battery comprises a core-shell structure, wherein the core of the core-shell structure is formed by Li<1+x>M<1-x-y1>ACO<2-z>, and the shell is formed from Li<1+x>M<1-x-y2>AC<2-z>, wherein M is at least one of Ni, Co and Mn, A is a doping element, C is a coating element, -0.05<=x<=0.1, 0<=y<=0.01, 0.03<=y2<=0.05, and 0<=z<=0.05. According to the positive electrode material provided by the invention, the L3/L2 ratio of the Ni of thecentral part material of the core-shell structure can be higher than that of the Ni of the surface part material through a doping and surface coating modification method, so that the positive electrode material has higher capacity, better rate capability and longer cycle life.