The invention discloses a nano-iron compound/intermediate-phase carbon microsphere composite material and a preparation method thereof, in the composite material, a nano-iron compound is uniformly dispersed, coated or embedded in intermediate-phase carbon microspheres, and the mass fraction of the nano-iron compound is 0.1%-10%. The preparation method comprises the following steps: uniformly dispersing an oil-soluble iron precursor and a sulfur additive in asphalt, carrying out a thermal polymerization reaction under the conditions of proper temperature, pressure and inert atmosphere protection, separating a product to obtain a composite material precursor, and further carbonizing to prepare the nano iron compound/mesophase carbon microsphere composite material. The preparation method hasthe advantages that the oil-soluble iron precursor forms uniformly dispersed nanoparticles in situ, so that the formation of a high-quality mesophase carbon microsphere composite material is promoted,and the product yield and particle size can be regulated and controlled. The lithium ion battery negative electrode material prepared from the composite material has good electrochemical characteristics.