In this study, the effect of changing the parameters of membrane fabrication, adding nanoparticles to the substrate, and also adding a second active layer containing nanoparticles on controlling the challenges of forward osmosis (FO) process and improving water flux has been investigated. In the first stage, in order to investigate the impact of the structural parameters of the substrates on the performance of the membranes, thin film composite (TFC) FO membranes with polycarbonate (PC) and polyether sulfone (PES) as substrates were fabricated. The substrates were prepared by Loeb-Sourirajan method. After preparing suitable substrates, active layers were fabricated via interfacial polymerization (IP) technique. The performance and characterization test showed that PC ca be a relatively hydrophilic polymer with a good property for use as a substrate of FO TFC membrane but as the result of gas permeability test shows, this membrane has large surface pore size in comparison with PES membrane. Then, TFC hollow fibers (HFs) were fabricated by an in-situ coating of polyamide layer on the lumen side of PVC/PC blend substrates for desalination by FO. Particularly, the substrate HFs were spun at two air gap distances of 2 and 6 cm, to investigate the effect of the air-gap distance on the FO performance. As the air gap distance increases, the surface pore size and the effective surface length decrease. Also, with increasing air gap distance, the surface and overall porosity increase and as a result, the pure water flux of substrate increases. Furthermore, the effect of HF length on the FO water flux was investigated. The results showed that the novel TFC HFs exhibited good FO performance. The longer the air gap distance, the better becomes the FO performance, in terms of simultaneous water flux and alginate fouling resistance, while the effect of the HF length remains a controversial issue. After selecting the optimal conditions (air gap) for the fabrication of the substrate,