A method for preparing a carbon powder from an organic polymer material and a method for detecting the crystal morphology in the organic polymer material. A method for preparing a carbon material product comprises a carbonization step in which: a straight-chain polymer material containing nanoscale crystals is carbonized by using a strong oxidizing agent free of heavy metal ions, thus acquiring a nanoscale carbon material. Also disclosed is a method for acquiring either a material having a carbonized surface or a powder material containing graphene by using an acid in treating the organic polymer material.