The invention discloses a medicine for treating a piglet edema disease and a preparation method thereof. The medicine is prepared from luisia morsei, loosestrife, chinaroot greenbrier, all-grass of twocolor velvetplant, pilea cavaleriei, abelmosk, Chinese starjasmine stems, cordate houttuynia, acmella ciliate, polygala tenuifolia, sweet basil, herb of dewberryleaf cinquefoil, oxalis rubra, Acorus gramineus Soland. var. pusillus Engl., f. suaveolens C. Y. Cheng, mss., ardisia japonica, inula cappa, Chinese alpine rush, tanoak bark, flower of Aglaia odorata Lour., Neolitsea chuii seeds, cardinal flower, Circaea lutetiana Linn. subsp. quadrisulcata (Maxim.)Asch.& Magnus, agilawood, henry clematis root, cortex acanthopanacis, hairyvein agrimony and Chinese dates. The medicine has the advantages that treatment principles are removing toxicity for detumescence and freeing lung for diuresis, the auxiliary principle is invigorating spleen to eliminate dampness, the treatment effect on the piglet edema disease is significant, the resistance ability of piglets can be enhanced, the treatment course is short, the treatment effect is good, medicine tolerance is avoided, no medicine residue exists, and the medicine is safe, convenient to use, easy to prepare, low in cost and capable of effectively controlling the illness state.