The invention relates to the field of medicinal preparations, particularly relates to a traditional Chinese medicinal decoction for treating scarlet fever, which is prepared from the following raw materials in percentage by weight: 7-10% of Arctium lappa fruit, 4-7% of Radix Bupleuri (Bupleurum chinense and / or Bupleurum scorzonerifolium), 4-6% of Physalis alkekengi, 4-7% of Herba Dendrobii, 5-8% of Scutellaria baicalensis, 4-6% of Polygonatum odoratum, 3-6% of Belamcanda chinensis, 4-6% of Gardenia jasminoides fruit, 2-3% of Cortex Moutan Radicis, 3-5% of Rehmannia glutinosa, 4-7% of Spirodela polyrrhiza, 6-9% of Cannabis sativa seed, 5-8% of Ophiopogon japonicus, 4-6% of Prunella vulgaris, 7-9% of Forsythia suspensa, 5-7% of Scrophularia ningpoensis, and 2-5% of Flos Lonicerae. The preparation method of the traditional Chinese medicinal decoction includes soaking the above raw materials in water, decocting, filtering to remove residues, and collecting filtrate. The traditional Chinese medicinal decoction can treat scarlatina, has the advantages of high efficacy, no allergic or toxic reaction, and no adverse side effect, can treat scarlet fever with high therapeutic effect and can prevent allergic reactions.