The invention discloses a 
drug for treating a 
cancer as well as a preparation method and application thereof. The 
drug is prepared from the following raw materials in parts by weight: 3-7 parts of 
prednisone, 5-12 parts of 
aminophylline, 6-10 parts of 
butylphthalide, 1-3 parts of 
promethazine and 11-19 parts of maltotriitol. The preparation method comprises the following steps: mixing the 
prednisone and 
aminophylline, then adding deionized water, and carrying out ultrasonic treatment for 20min at the temperature of 45 DEG C to prepare a mixture A; mixing the 
butylphthalide and the 
promethazine, then adding the deionized water, and carrying out 
microwave treatment for 5min to prepare a mixture B; and mixing the maltotriitol, the mixture A and the mixture B, carrying out ultrasonic treatment for 10min at the temperature of 65 DEG C, and then stirring the mixture at the temperature of 60 DEG C to dry to obtain the 
drug. The drug is used for treating the 
cancer, particularly has a unique 
curative effect on treating 
leukemia, is simple and available in raw materials, simple in preparation technology and low in production cost, does not have side and toxic effects and is suitable for large-scale popularization.