Polyacrylonitrile (PAN) is a popular material in membrane field because of its excellent mechanical property, thermal stability, and chemical resistance. Unfortunately, PAN nanofibers produced by electrospinning are not suitable for interfacial polymerization process directly due to its hydrophobicity and large average pore size. In this work, the cross-linked chitosan (CS) solution was coated on the nanofiber surface to fabricate a sublayer, based on which thin-film composite (TFC) membranes were prepared using m-phenylenediamine and 1,3,5-trimesoyl chloride as the monomers. The impact of the different sublayers on the performances of TFC PAN nanofiber membranes for forward osmosis (FO) was studied by varying cross-linked CS concentrations. The results indicated that the increased CS concentration not only led to the relatively denser polyamide layer, but also changed its morphology. In the reverse osmosis process, NaCl rejection increased from 46.5 to 83.5%. Salt flux from feed solution to draw solution decreased from 25.8 to 8.9 g·m-2·h-1 (0.1 M NaCl solution as feed, 2 M glucose solution as draw solution, FO mode). This study found that the sublayer had noteworthy impact on the separation layer and helped us to pave the way to design high-performance FO membranes.