A method for preparing artificial graphite includes (A) preparing heavy oil, and forming coke from the heavy oil through continuous coking reaction such that the coke has a plurality of mesophase domains, wherein a size of the mesophase domains ranges between 1 and 30 μm by polarizing microscope analysis; and (B) processing the coke formed by step (A) sequentially by pre-burning carbonization treatment, grinding classification, high-temperature carbonization treatment and graphitization treatment to form polycrystalline artificial graphite from the coke. The method for preparing artificial graphite of the present invention and the polycrystalline artificial graphite prepared thereby are applicable to batteries.