The solubilites of 5,10,15,20-tetrakis(p-chlorophenyl)porphyrin (abbreviated in p-ClTPP) in binary propionic acid-rich propionic acid + water solvent mixtures from (293.2 to 353.2) K were measured. The effects of mass fraction of propionic acid from (0.80 to 1.00) in propionic acid + water mixtures on the solubility were studied. The results show that the solubilites decrease with the decreasing mass fraction of propionic acid at constant temperature, and increase with the increase of temperature at constant solvent composition. The Apelblat equation was used to correlate the experimental data, and the solubilities calculated by the equation were in good agreement with experimental observations. In addition, the thermodynamic parameters for the solution of 5,10,15,20-tetrakis(p-chlorophenyl)porphyrin in propionic acid + water mixtures including dissolution enthalpy, entropy, isobaric heat capacity, and Gibbs energy were calculated by the Clark and Glew equation.