The invention relates to a drug for treating cancer and a preparation method thereof, belonging to the technical field of the drug and the preparation method thereof. The drug is characterized by comprising the following raw materials: 10000 portions of white wine matched with 8 to 12 portions of musk, 10 to 20 portions of capillary wormwood herb, 10 to 20 portions of artemisia princeps and prepared common monkshood daughter root, 10 to 20 portions of manchurian wildginger, 10 to 20 portions of cochinchina momordica seed, 10 to 20 portions of kusnezoff monkshood root, 15 to 25 portions of realgar,15 to 25 portions of ginseng, 1800 to 2200 portions of ophiorrhiza pumila, 800 to 1200 portions of barbed skullcap herb, 250 to 350 portions of Chinese toon root and 1800 to 2200 portions of garlic. The preparation method comprises the following steps of: 1) matching 10000 portions of white wine with 1800 to 2200 portions of garlic and soaking for 10 to 15 months; 2) screening, drying, weighing and disinfecting the ingredients of the drug, grinding realgar into fine powder, putting the obtained mixture in the white wine obtained from the step 1 according to required matching ratio for 10 to 20 days; 3) weighing musk according to matching ratio and grinding the musk into powder for future use; and 4) taking 500 portions of medicated liquor obtained from the step 2) to be matched with 0.3 to 0.8 portion of musk powder, mixing evenly and taking. The drug has good effect for treating cancer in early stage and middle stage, and preventing cancer; and the curative rate of the cancer in early stage is more than 90 percent.