Crystallization in the presence of high pressure gas as antisolvent could be applied for the recovery of valuable compounds from liquid solution. A study of separation behavior is presented here for a mixture of anthracene (AN) and anthraquinone (AQ) in cyclohexanone (CX) expanded with a gaseous antisolvent, CO2. The pressure range was 0.1 to 12 MPa; the temperature was either 292 or 313K. Separation factors were obtained from the measured salted-out yields and the supersaturation of each solute could be also obtained for this pressure-tuning crystallization. The separation factor varies almost linearly with relative supersaturation ratio in the crystallization of anthracene-anthraquinone from cyclohexanone and CO2.