Abstract: In this study, coamorphous simvastatin-gliclazide was prepared and characterized. Its single-phase amorphous nature was demonstrated. The hydrogen bond between the O-H group of simvastatin and sulfonylurea C=O group of gliclazide was revealed to be the trigger for the amorphization of gliclazide, which is difficult to form an amorphous state in other methods. Coamorphous simvastatin-gliclazide can significantly enhance the solubility and dissolution of gliclazide, without obvious effect on simvastatin. Compared with amorphous simvastatin, coamorphous simvastatin-gliclazide showed improved physical stability in the cunrent study.