The invention discloses a method for preparing a porphyromonas gingivalis culture medium for plaque specimens. The method is characterized in that the formula for preparing 1000ml of culture medium contains malt extract, egg protein fluid, heme chloride solution, vitamin K1 ethanol solution, magnesium citrate, agar, synercid, telithromycin, linezolid and asparagines, and distilled water added to 1000ml. The preparation method of the optimized formula comprises the steps of dissolving the malt extract, the egg protein fluid, chlorhematin, agar, magnesium citrate, calcium citrate tetrahydrate, synercid, garlic extract juice and L-cysteine into rhizoma polygonati boiling liquid; evenly mixing, fixing the volume and charging after sterilizing. Compared with the prior art, the porphyromonas gingivalis culture medium has the characteristics of detection reliability and high porphyromonas gingivalis separation rate.