The laser monitoring observation technique was used to study the solid–liquid equilibrium solubility data of bis(2-hydroxyethyl) terephthalate (BHET) in four binary mixed solvents (methanol + water, ethanol + water, ethylene glycol + water, and acetone + water) from 283.15 to 323.15 K at normal atmospheric pressure. Five thermodynamic models (the Apelblat model, the λhmodel, the Jouyban–Acree model, the Wilson model, and the NRTL model) were selected to correlate the experimental data. Based on the correlation index and the root-mean-square deviation, the Apelblat model and λhmodel were more suitable for fitting the BHET solubility data. According to the obtained Wilson model parameters, the thermodynamic properties during the dissolution of BHET were calculated. The results showed that the dissolution process of BHET in all mixed solvents was spontaneous.