The solubility of aluminum sulfate in sub- and supercritical water (SCW) has been measured using a flow system at temperatures and pressures ranging between (619 and 675) K and (15 and 29.2) MPa, varied from 1.61.10(-5) to 2.94.10(-5) under the conditions studied in this respectively. Experimental solubility values (in terms of mole fraction) varied from 1.61.10(-5) to 2.94.10(-5) under the conditions studied in this work. These data have been fitted by response surface methodology (RSM) obtaining values for an average percentage deviation (APD) of 6.2 %. To extend temperature and pressure ranges analyzed, a theoretical solubility model based on the Flory-Huggins approach was applied, leading to worse predictions than the previous model. Subsequently, some additional empirical and semiempirical approaches were also used for the description of the solubility. As a result, a very simple approach (a polynomial function of fluid density) reached an accuracy even better (APD = 5.8 %) than the more complex polynomial model derived from response surface methodology.