The invention discloses a compound traditional Chinese medicine granule for treating oral ulcer and a preparation method thereof. The compound traditional Chinese medicine granule is prepared from the following raw materials in parts by weight: honeysuckle, panax notoginseng, radix sophorae flavescentis, coptis chinensis, burdock, liquorice, dried radix rehmanniae, asarum sieboldii, fructus forsythia, dandelion, cortex phellodendri, fructus evodiae, astragalus membranaceus, radix ophiopogonis, aloe, ajuga decumbens thumb, rhizoma belamcandae, pericarpium citri reticulatae, rheum officinale, dendrobium, agastache rugosus, amber and borneol. The preparation method of the compound traditional Chinese medicine granule for treating oral ulcer comprises the following steps: extracting volatile oil of honeysuckle, astragalus membranaceus, fructus forsythia and radix sophorae flavescentis; decocting with dregs and other traditional Chinese medicines for three times; and mixing each filtrate and then carrying out vacuum concentration to prepare the granules. The preparation disclosed by the invention has the efficacies of clearing away heat and toxic materials, relaxing spasm, relieving pain, healing sores and promoting tissue regeneration, is free of toxic or side effect, simple to prepare, fast to take effect, and high in ulcer healing speed, and is capable of enhancing and regulating the immunity of the organism, so that the effects of fastness to take effect and treating both symptoms and root causes are really realized.