The invention discloses a graphite powder of the cathode of a lithium ion battery, and a preparation method thereof; the technical problem to be solved is that the transmission speed of a lithium ion and an electrolyte to the inside of the electrode needs to be increased. The graphite powder of the cathode of the lithium ion battery of the invention has the microscopic feature of massive, spherical and near-spherical shapes and has the characteristics of nano-porous. The preparation method thereof comprises the following steps of: grinding, adding coating modifiers or / and catalysts, mixing, dissolving, and carrying out preheating treatment and heat treatment. Compared with the prior art, the invention carries out modifying treatment to graphite material and realizes the characteristic of nano-porous by adding pore-forming agents, thus being beneficial to the transmission of the lithium ion, improving the liquid-absorbing performance of a pole piece after compaction, reducing the content of impurity in the graphite, improving the liquid-absorbing performance and the magnification performance of the graphite material, meeting the requirements of the lithium ion dynamic battery for the compatibility and the charging and discharging performance with large magnification of the electrolyte of the graphite material and having the advantages of lower production cost, simple technique and easy industrialization.