The invention relates to a gargle for treating recurrent aphthous ulcer and periodontitis and a preparation method of the gargle. The preparation method of the gargle comprises the following steps: soaking honeysuckle, asiatic moonseed rhizome, glaucescent fissistigma roots, gynostemma pentaphyllum, conic gymnadenia rhizome and rose mallow roots, and performing water extraction and alcohol precipitation on the six ingredients, taking toad venom and soaking toad venom with alcohol, extracting, adding a certain proportional quantity of an anti-caries sweetening agent, an acid regulator, a preservative and an appropriate amount of water after taking menthol and adding an appropriate amount of ethanol for dissolving, uniformly mixing, sterilizing and filtering. The gargle has the advantages that the formula is reasonable, the ingredients are easy to obtain, the production technology is simple, the reproducibility is good, the curative effect is remarkable, toxic or side effects are small, recurrent aphthous ulcer and periodontitis (gingivitis and periodontitis) are treated, symptoms, such as oral ulcer, exudation, hyperaemia, hemorrhage, edema and pain, caused by recurrent aphthous ulcer and periodontitis, can be markedly eliminated, recurrent aphthous ulcer and periodontitis are difficult in recurring, the taste is good, and the gargle is suitable for people of all ages.