A new separation technology, supercritical fluid extraction, has been applied for advanced refining of fluid catalytic cracking-decant oil (FCC-DO) to improve the quality of carbon precursor used for production of high performance carbon materials. The pseudo-binary P-x-y phase behaviors were investigated with a continuous-flow type apparatus at 493.2, 513.2, 533.2, and 553.2 K, while the pressure was changed from 1 to 4.5 MPa. Besides, the dependence of temperature and pressure to extraction behavior and selectivity has been investigated. The pseudo-binary phase behaviors and extraction selectivity were successfully predicted with the Peng-Robinson equation-of-state with considering interaction parameters between hexane and pseudo-components of FCC-DO. The phase diagrams of the system has been classified follow the category of phase boundary diagram models. The increasing of extraction temperature was effective for selective rejection of heavy end from FCC-DO, while the increasing of extraction pressure showed advanced effect on certain limited condition. The multiple staged extraction system is suggested for more effective refining of FCC-DO.