The simulation of Eulerian multiphase flow model with two-phase (air & water) in membrane bioreactor were aimed at obtaining and comparing gas hold-up distribution, velocity field and membrane surface rate among the two reactor internal configuration of “alignment” and “alignment” diversion. Furthermore, the gas distribution mode was analyzed as well as optimized. The mini-model experiment was conducted to validate the simulation result. It is shown that: the bubbles track of internal field tended to flow to the membrane assembly center position, and then dispersed on the top of membrane modules in the two reactor configurations; the influence of diversion on gas holdup distribution was in apparent while notable on the velocity field distribution. The simulation results of an experimental model shrunk 100 times was proved to be consistent with the experimental results. Through an optimization simulation of gas distribution mode, the non-uniform gas distribution mode was proved that it can improve the range of gas distribution and the turbulence intensity.