Hydrophobic ZSM-5 zeolite filled polydimethylsiloxane (PDMS) composite membranes with Nylon micro-filtration membrane as the support layer were prepared to separate acetaldehyde from its aqueous solution. The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. Their structural morphology and thermal stability were also examined. The swelling study showed that the composite membranes presented higher degree of swelling in aqueous solution of acetaldehyde than in pure water at 25 degrees C, suggesting that the membranes have stronger sorption capacity in acetaldehyde solution. The effects of ZSM-5 filling content and acetaldehyde concentration on pervaporation performance of composite membranes were investigated. The permeation experiments at different temperatures showed that both selectivity and permeation flux of composite membranes increased with temperature. With 5%ZSM-5-PDMS/Nylon membrane at acetaldehyde mass concentration of 8% and 25 degrees C, the separation factor of acetaldehyde/water achieved 35 and the permeation flux was 233.3 g.m(-2).h(-1).