The invention provides a preparation method of a nano porous metal oxide/carbon lithium ion battery cathode material. The preparation method comprises the following steps: firstly, weighting ferric salt or manganese salt and carboxylate organic ligands, and putting into a high-pressure reaction kettle; and after a polar solvent is added and dissolved, carrying out a hydrothermal reaction for 10-72h at 100-180 DEG C to generate a transition metal coordination polymer precursor; and after the transition metal coordination polymer precursor is washed and dried, decomposing the precursor for 0.5-6h at a temperature of 300-600 DEG C in an inert atmosphere in a tube furnace, thus obtaining a nano porous metal oxide/carbon lithium ion battery cathode material containing iron oxides or manganese oxides. According to the preparation method, since the transition metal coordination polymer precursor which is structurally designable and controllable is used as a template-type precursor, a nano porous metal oxide/carbon lithium ion battery cathode material is obtained by using an in-situ thermal decomposition method. The method is simple in process, and the obtained products have the advantages of high electrical conductivity, high specific capacity, good cycle stability, excellent high-ratio discharge performance and high energy density.