The invention discloses a medicine for treating tumors and a preparation method thereof. The medicine is prepared from rattlesnake fern, oldenlandia diffusa, Franxinus pistacifolia Feng, mss., curcuma zedoary, codonopsis pilosula, gynostemma pentaphylla, acmella ciliata, barbed skullcap herb, physalis angulata, Chinese loropetalum herb, rattlesnake plantain, poria cocos, herb of glabrous sarcandra, lucid ganoderma, the root of wilford swallowwort, Hainan ervatamia root, hibiscus syriacus, platycarya strobilacea fruits, scutellaria indica, ligusticum wallichii, caulophyllum robustum, fructus forsythiae, seaweed, pseudo-ginseng, arsenic ore, folium sennae and benzoin. The medicine has the advantages of achieving the effects of removing toxic materials and stasis, dispersing swellings, dredging collaterals and removing tumors and smoothening qi and blood, becoming effective rapidly, being high in effective rate, clear in treatment effect, short in treatment course, free of toxic and side effects and low in price, and the like; in addition, the medicine can suppress tumor growth, the tumor suppression rate is increased along with increasing of dosage, the proliferation activity of tumor cells is disturbed, and the anti-tumor effect is achieved.