Abstract: Spironolactone, a class Ⅱ drug of the biopharmaceutics classification system, has low oral bioavailability due to poor solubility. Spironolactone solid dispersions were prepared using the solvent method in order to improve its aqueous solubility. Optimization studies of spironolactone solid dispersions were performed using in vitro dissolution tests. Differential scanning calorimetry, X-ray diffraction and Fourier transform infrared were used to investigate the physical state of the drug in carrier materials and to detect the possible interactions between the drug and carrier materials in the solid dispersions. In addition, stress tests were employed to elucidate the key factors which have influence on the stability of the spironolactone solid dispersions. Results showed that spironolactone in the solid dispersions formulated with Soluplus and HPMC-E5 were both in amorphous state and the hydrogen bonds between the drug and carrier materials were formed in the solid dispersion. Therefore, the in vitro dissolution of spironolactone was also significantly enhanced. Stress tests demonstrated that the physical stability of spironolactone solid dispersions prepared with Soluplus was greatly improved compared to those formulated with HPMC-E5. Thus, spironolactone solid dispersion formulated with Soluplus using the solvent method could be used to improve the in vitro dissolution and stability of poorly soluble drugs.