The invention discloses a pharmaceutical composition for treating diabetes and its preparation method and application. The pharmaceutical composition comprises the following raw materials in parts by weight: 3-5 parts of astragalus, 2-2.5 parts of salvia miltiorrhiza, 1-2 parts of rehmannia glutinosa, 2-3 parts of bitter gourd, 1-2 parts of polygonatum, 2-3 parts of coptis, 0.5-1 part of Atractylodes macrocephala, 0.8-1.5 parts of Polygonatum, 0.5-1 part of Scutellaria baicalensis, 2-3 parts of trichosanthin, 1.5-3 parts of raw gypsum, mulberry 2‑3.5 parts of root, 2‑3.5 parts of dendrobium, 2‑4 parts of Chinese yam, 1‑2 parts of capillary, 2 parts of cash cow leaves, 1‑2 parts of cinnamon bark, 2‑3 parts of black tea, 3‑5 parts of dried potatoes, 1.5-2 parts of grape seeds, 1-1.5 parts of cheese, 2-3 parts of wheat bran, 2-2.5 parts of seaweed. The pharmaceutical composition of the present invention can control complications by invigorating the kidney and increasing resistance, activating collaterals and invigorating the heart, reducing blood pressure and removing fat; balancing body constitution by balancing cold and heat, unblocking the middle and harmonizing the body, nourishing qi and nourishing blood; , Improving insulin sensitivity to carry out targeted therapy to repair islet function; it can effectively treat diabetes, and the curative effect is significant.