The invention provides a cathode material of a lithium ion battery. The cathode material is composed by the atomic ratio shown in formula (I): Lia(MxMn2-x)(O4-yZy), wherein a is greater than or equal to 0.8 and less than or equal to 1.2; x is greater than or equal to 0 and less than or equal to 1; y is greater than or equal to 0 and less than or equal to 1; M is one or more selected from Li, Na, K, Ca, Mg, Al, Ti, Sc, Ge, V, Cr, Zr, Co, Ni, Zn, Cu, La, Ce, Mn, Hf, Nb, Ta, Mo, W, Ru, Ag, Sn, Pb and Si; and Z is one or more selected from OH, halogens, N, P, S and O. Primary particles of the cathode material have sphere-like morphologies, wherein (111) face is connected with adjacent equivalent crystal face through a curved surface having no clear edges. The invention also provides a preparation method for the cathode material of the lithium ion battery and the lithium ion battery. The cathode material provided by the invention has good high-temperature cycling performance and good filling property.