The invention relates to a Chinese patent medicine for treating diabetes mellitus. The Chinese patent medicine for treating diabetes mellitus is prepared from the following raw materials in a proportion: 3 to 6kg of bock greenbrier rhizome, 2 to 4kg of dried fruits of bitter gourd, 1 to 2kg of radix salviae miltiorrhizae, 1 to 2kg of radix astragali seu hedysari and 0.1 to 0.2kg of roots of American ginseng. The effects of clearing away heat and toxic materials, promoting blood circulation to remove blood stasis, invigorating the spleen, supplementing qi, lowering blood glucose, activating the human dormant pancreas and promoting the pancreas islet function rehabilitation are achieved.