Solubility data for the K2CO3 + K2CrO4 + H2O system at 40 degrees C, 60 degrees C, 80 degrees C, and 100 degrees C were determined, and the phase diagram at 100 degrees C was constructed. Furthermore, the crystallization areas in the phase diagram were elaborately analyzed and discussed. On the basis of the solubility data, a separation method of potassium chromate from the K2CO3 + K2CrO4 + H2O system for the cleaner production of potassium dichromate by carbonating process using carbon dioxide was evaluated.