The experiments were carried out to separate formaldehyde wastewater by pervaporation with PDMS/CA composite membranes. The influence of feed temperature and feed concentration of formaldehyde aqueous solution on the permeation flux and separation factor of formaldehyde was investigated thoroughly. Experimental results have indicated that there is an optimal separation factor for pervaporation process over a range of temperatures. When dealing with formaldehyde wastewater with feed concentration of 1% at 50℃ and under permeation pressure of 13KPa, this composite membrane can reach excellent separation efficiency with up to 110 g/（m2•h）of flux and up to 1.75  of separation factor. Under this condition, permeation flux decreases linearly and separation factor also reduces when the permeation pressure increases. Besides, the higher the concentration is, the larger the permeation flux is, but there is no obvious change on the separation factor. Apparent activation energy of the composite membrane could also been achieved by Arrhenius equation and the calculated value is considered as 27.57KJ/mol. Compared with other methods of separating formaldehyde wastewater, pervaporation has such many advantages as simple equipment, convenient operation and low cost , which can offer a new and effective technical attempt for industrial application of formaldehyde wastewater treatment.