The invention discloses a composite material, a preparation method of the composite material, and a lithium ion battery comprising the composite material, and belongs to the field of lithium ion battery materials. The composite material is in a core-shell structure. A shell layer of the composite material comprises a middle layer and an outer layer coated outside the middle layer. An inner core of the composite material is Li(NixCoyAlz)O2; the middle layer is Li(Ni1/3Co1/3Mn1/3)O2; the outer layer is LiNi0.5Mn1.5O4; and a molar ratio of the inner core to the middle layer to the outer layer of the composite material is a:b:c, wherein a+b+c=1, b is greater than 0 and less than 0.5, c is greater than 0 and less than 0.5, x+y+z=1, y=0.15, and z is greater than or equal to 0.03 and is less than or equal to 0.05. The composite material has the characteristics of comparatively high capacity, low alkalinity and electrolyte resistance, has good cycling stability and safety performance, has an obvious cost performance advantage, and is more suitable for application of a power battery. Structural precursors of the layers of the composite material are sequentially formed by utilizing a coprecipitation synthesis technology, so that good consistency and good homogeneity are achieved and the layers are tightly connected with each other. Besides, the composite material can be obtained by a single roasting process; and the cost can be lowered effectively.