The invention provides a molybdenum disulfide/polyaniline composite material, a preparation method thereof, a lithium ion battery cathode and a lithium ion battery. The preparation method of the molybdenum disulfide/polyaniline composite material comprises the steps of preparing polyaniline dispersed with molybdate, performing ahydrothermal reaction on polyaniline dispersed with molybdate and a sulphur source, and the like. The molybdenum disulfide/polyaniline composite material prepared by the preparation method of the molybdenum disulfide/polyaniline composite material is steady in structure and good in conductivity, when the molybdenum disulfide/polyaniline composite material taken as a lithium ion battery negative electrode material is applied to the lithium ion battery, a device is endowed with excellent rate capability and circulatory stability capability, and the lithium storage capacity is high.