The invention relates to a rhein-
arginine eutectic compound, and a preparation method, a purification method and application thereof in preparation of medicines for treating diabetic complications. The rhein-
arginine eutectic compound is an eutectic substance formed by rhein and L-
arginine, the mol ratio of the active
medicine component of the rhein to the L-arginine is 1:1, and the X-
ray diffractogram of the eutectic
powder has the characteristic peaks of 9.22 degrees, 10.34 degrees, 12.28 degrees, 26.05 degrees, 26.58 degrees and 27.57 degrees 2theta. The medicines for treating diabetic complications are medicines for treating diabetic cardiopathy, medicines for treating diabetic macroangiopathy, medicines for treating
diabetic nephropathy, medicines for treating diabetic orchiopathy, medicines for treating complicated
male sexual dysfunction of diabetes, or medicines for treating diabetic impotence. The invention can increase the
solubility and
dissolution of the medicines, enhance the purity and stability of the rhein-arginine eutectic compound, reduce the
impurity content and hygroscopicity, enhance the
bioavailability and improve the release characteristic.