Membranes are capable of separating species as a function of their physical and chemical properties when a driving force is applied, which enables filtration for removal of colloids, cells and molecules. In this work, flat sheet polysulfone ultrafiltration membranes were cast due to polysulfone's high mechanical strength, thermostability and stability against chemicals. The main goal was to investigate the effects of dope concentration, membrane thickness and inorganic additive, lithium chloride (LiCl), on the filtration of different salt concentrations. The results revealed that with increasing dope concentration and membrane thickness, permeability decreased and subsequently salt rejection increased. Furthermore, compared to LiCl-free membranes, LiCl-containing ones were more permeable and displayed higher salt rejection, which was due to more porosity and smaller pore size caused by LiCl additives in membranes.