The fluid patterns and structure optimization of a novel continued-flow integrated biological reactor (CIBR) were explored by using the computational fluid dynamics (CFD). The results of the CFD simulation revealed that both the liquid velocity field and the gas volume fraction in the CIBR showed an axisymmetric spatial distribution. Furthermore, increasing the aperture sizes of below diversion holes from 2 cm to 8 cm could significantly enhance the turbulent kinetic energy of three-phase separation zone. Consequently, the solid-liquid separation and the treatment efficiency of CIBR were enhanced. In addition, an increase in the angle of the inclined plate (from 35° to 45° and further to 50°) caused increases in the liquid velocity, volatility and gas holdup in the threephase separation zone, while decreased gradually in the settling zone. These changes improved gasliquid separation in the three-phase separation zone and the sludge sedimentation in the settling zone. The findings of the study provide an insight into the fluid characteristics of gas-liquid-solid three phases within the CIBR.