Abstract: Numerical simulations are performed for investigating the mixing/segregation of flotsam component (FC) and jetsam component (JC) of binary mixture in supercritical water fluidized bed (SCW FB). The collisional interactions of FC and JC are modeled by means of the unequipartition of granular energies-based kinetic theory of granular mixture (KTGM). The distributions of segregation index are predicted at different SCW pressures and temperatures. Four regions named as the segregation (SE), dense (DE), transition (TR) and freeboard (FR) are defined along bed height. The synergy angle is proposed to measure the compromise in competition of mixing/ segregation of FC and JC along bed height. The synergy angles are determined from volume fractions of FC and JC in the DE region. The effect of SCW temperature and pressure on synergy angle and segregation index is investigated. The simulated results are analyzed according to the SCW pressure and temperature as well as inlet SCW fluidizing velocities. The simulated results suggest that the increase of SCW temperature and fluidizing velocity contribute the mixing of FC and JC binary mixture along bed height of SCW FBs.