The invention discloses a pharmaceutical composition for preventing and treating chronic swine plague and a preparation method of the pharmaceutical composition. The pharmaceutical composition comprises the following raw Chinese medical materials: gypsum rubrum, jasmine, dried radix rehmanniae, cacumen biotae, moutan bark, rhizoma phragmitis, radices trichosanthis, lophatherum gracile, dayflower, phoenix-tail fern, polygonum aviculare, dandelion, lotus leaf, lotus plumule, radix ophiopogonis, fructus forsythia, radix scrophulariae, liquorice, Chinese eriosema root, dicliptera chinensis, bryoniifolia, adenophora trachelioides maxim., Indian melothria root, cynanchum thesioides, trichosanthes kirilowii maxim, tuberous sword fern tuber, giant clam meat and yam rhizome. The pharmaceutical composition mainly takes effects of clearing away heat and toxic materials, cooling blood and promoting the secretion of body fluid and also has auxiliary functions of invigorating spleen and supplementing qi, so as to reconcile yin and yang, and qi and blood of pigs with chronic swine plague to finally treat swine plague; the pharmaceutical composition for preventing and treating chronic swine plague has the advantages of short treatment course, relatively good effect, low residual quantity and good environment friendliness and simultaneously is capable of enhancing the immunity and the disease resistance of pigs.