A novel crystalline form of Cefathiamidine compound and its preparation method, characterizing in its X-ray powder diffraction pattern and differential scanning calorimetry thermogram. Dissolving Cefathiamidine compound with a purity of 98% or higher in a solvent at a temperature of 30˜45° C. to form a solution, whose concentration is controlled within 0.05˜0.2 g/mL, and then adding a solventing-out agent to the solution, wherein the amount of the solventing-out agent is 3˜5 times (in volume) of that of the solvent; followed by cooling the solution down to 0˜10° C. at a rate of 0.2˜1° C./min; continuing to stir for 1˜3 hours, and separating the obtained solid-liquid suspension to provide a novel crystalline form of Cefathiamidine compound after drying.