The invention discloses a preparation method of artificial graphite and a lithium ion battery. The preparation method of the artificial graphite comprises the following steps: S10, carrying out graphitization treatment on raw material coke powder to obtain an intermediate; s20, uniformly mixing a second raw material with the intermediate to obtain a composite precursor; amd s30, carrying out carbonization treatment on the composite precursor at 900-1400 DEG C under the protection of protective gas to obtain artificial graphite; wherein the second raw material comprises a liquid-phase coating agent. Through liquid phase coating, the surface morphology of the artificial graphite can be effectively improved, the specific surface area is reduced, active sites of side reactions are reduced, gas production of the lithium ion battery is reduced, volume expansion is reduced, and the safety performance of the lithium ion battery is improved; in addition, graphitization treatment is performed firstly and then coating is performed, so that the prepared artificial graphite has relatively good liquid absorption performance, the internal resistance is reduced, the low-temperature performance is improved, the reduction of the internal resistance is beneficial to the movement of lithium ions, and the prepared lithium ion battery has relatively good fast charging performance.