The equilibrium solubility of amidinothiourea (ATU) in monosolvents, including N-methyl-2-pyrrolidone (NMP), acetone, 1,4-dioxane, acetonitrile, ethyl acetate, toluene, methanol, 1-butanol, 1-propanol, ethanol, 2-propanol, and cyclohexane, was determined by using a isothermal saturation method. The experimental temperature and pressure are 283.15-323.15 K and 101.3 kPa, respectively. The sequence of solubility from high to low is NMP > acetone > 1,4-dioxane > methanol > ethanol > acetonitrile > 1-propanol > ethyl acetate > 2-propanol > 1-butanol > toluene > cyclohexane. Two models (modified Apelblat equation and lambda h equation) were employed to describe the relationships between solubility of ATU in mole fraction and temperature, and the values of relative average deviations and root-mean-square deviations between the experimental and calculated solubilities were no more than 2.07% and 1.96x10(-4), respectively. The appropriateness of the models was evaluated by statistical analysis. Based on the results of statistical analysis, the two thermodynamic models can correlate the solubility of ATU in monosolvents very well. The interactions between solute and solvent and between solvent and solvent were studied to evaluate the influence of solvation interaction on solubility of ATU. The solubility of ATU in monosolvents was calculated by the Kamlet and Taft linear solvation energy relationship model (KAT-LSER). Interactions of dipolarity/polarizability and hydrogen-bond donor of the solvent with the solute are beneficial to improve the solubility of ATU. However, the cavity term, accounted by Hildebrand solubility parameter, is adverse to the solubility of ATU.