Forward osmosis (FO) is an emerging technology, however the internal concentration polarization (ICP) problem needs to be resolved in order to improve the water flux. Hydrophobic/hydrophilic interpenetrating network composite nanofibers (HH-IPN-CNF) was used for FO membrane support layer, which was successfully designed and fabricated by electrostatic spinning technology. Hydrophobic polymer is polyethylene terephthalate (PET) and hydrophilic polymer is polyvinyl alcohol (PVA). The FO membrane flux has a significant increase due to the HH-IPN-CNF support layer. The membrane flux improved with the increase of PVA nanofiber content in the HH-IPN-CNF support layer. When the ratio of PET/PVA composite nanofibers was 1/4, the FO membrane exhibited the highest water flux (47.2 LMH) and low salt leakage (9.5 gMH). In the test, deionized (DI) water was used as feed solution (FS), and 0.5 M NaCl solution was used as draw solution (DS) in the mode of active layer facing DS. The improvement of FO flux was attributed to the increase of wetting performance of support layer and the water-transferring function. The existence of the HH-IPN-CNF structure formed between PET and PVA nanofibers leads to the reduction of the ICP. The FO membranes with HH-IPN-CNF support layer achieved a significant increase in water flux. (C) 2014 Elsevier B.V. All rights reserved.