Abstract: Valsartan-hydrochlorothiazide co-crystals were prepared by a liquid-assisted milling method to improve the dissolution performance of the insoluble drugs.Samples of cocrystal, valsartan, hydrochlorothiazide powders and valsartan-hydrochlorothiazide mixtures were characterized by powder X-ray diffraction, Raman spectroscopy, infrared spectroscopy and other methods.The in vitro dissolution properties of Active Pharmaceutical Ingredient (API) in the above four samples were analyzed by high performance liquid chromatography.The results confirm the cocrystal formation of valsartan and hydrochlorothiazide, and show that the dissolution performance of the APIs in the cocrystal is significantly improved when compared with the bulk drugs.The two APIs had a tendency to dissolve synergistically in the cocrystal.The results provide a new option for the co-administration of valsartan and hydrochlorothiazide.