The invention discloses a traditional Chinese medicine combination for treating diabetes mellitus and a preparation method thereof; the traditional Chinese medicine combination is formed by eleven Chinese medicinal crop raw materials, that is, salvia miltiorrhiza, root of common peony, angelica, achyranthes, safflower, peach kernel, yam, root of rehmannia, radix glehniae, lily and radix ophiopogonis; the traditional Chinese medicine combination has the efficiency of promoting blood circulation by removing blood stasis and nourishing Yin and moistening dryness, remarkably reduces blood sugar levels, increases bodymass of diabetics, regulates blood fat, improves pathological changes such as blood capillary basilar membrane incrassation and microvascular endothelial cell hyperplasia caused by diabetes mellitus, increases blood flow volume and improves microcirculatory disturbance.