Based on the Euler three-phase model in Fluent, the improved drag model was applied to the two-dimensional unsteady numerical simulation of continuous three-phase airlift inner-loop bioreactor. The improved model was applied to simulating the time-averaged liquid velocity in the downcomer, the maximum liquid velocity, the gas holdups under different aeration rates and different volumes of sand and the diffusion process of phenol when the aeration rate was 10.2 L/min and the volume of sand was 2 L. The result showed the simulated values of liquid velocity, gas holdups and the diffusion process were consistent with the experiment results. Then the time-averaged liquid velocity in the downcomer was simulated with the improved model when the solid density was 1200, 1500, 1800, 2220 kg/m3, respectively, and particle sizes was 0.3, 0.6, 0.9 mm, respectively. The time-averaged liquid velocity increased with the solid density and the particle sizes decreasing.