Poly(ether-b-amide) (Pebax11657)/polyacrylonitrile (PAN) composite hollow fiber membranes for a potential use in CO2/CH4 separation were prepared by a new continuous coating method, referred to as cross-flow filtration. This technique allows to obtain the simultaneous coating of a large number of fibers, facilitating the scale-up. The dense layer was deposited in the lumen of the fibers allowing the coating of all the fibers in a single step. The coating on the inner surface of the fibers avoids the negative effects such as sticking or accidental mechanical damages occurring in the case of external coating. The membrane preparation was optimized by modulating different parameters. The optimal range of viscosity and concentration of the polymer solution to obtain a selective homogeneous Pebax1 layer was identified. The presence of the Pebax11657 dense layer was confirmed by IR spectroscopy and the morphology of the composite membranes was observed by SEM analysis. The gas separation performance of the membrane modules was determined by single gas permeation measurements. A preliminary optimization yielded membranes with PCO2 = 5x 103 (m3m2 h1 bar1), aCO2=CH4 = 18 equal to that of the neat dense polymer. The PEBAX1/PAN hollow fibers modules are potentially useful for application in the purification of biogas.