Abstract: Polystyrene composite membranes were prepared by using wood powder of 48µm or 150µm as filler. The effects of wood powder content, thickness of composite membrane and particle size of wood powder on the urea permeation capability of composite membranes were discussed. The result showed that the addition of wood powder could effectively adjust the urea permeation rate of polystyrene membranes and the urea permeation rate of polystyrene/wood powder composite membranes are obviously higher than that of polystyrene membrane. The urea permeation rate of composite membranes increased with increasing wood powder content gradually. Optics microphotographs showed that microfibril structure within wood powder was obvious, wood powder in composite membrane swelled and became the fast permeation channels for urea when the composite membrane was immersed in water.