Three types of membranes have been studied; ES10 (reverse osmosis membrane), LES90 (nanofiltration membrane), and improved LES90 for the analysis of the improvement of membranes by tannic acid. We assumed that ES10 had a uniform structure without any pores, LES90 had a normal section and a defective section, and that In improved LES90, most defects were improved by tannic acid. We calculated the membrane transport parameters for it normal section using a best-fit method based on the Spiegler-Kedem equation, and for a defective section using the Steric Hindrance-Pore model for neutral solutes and the Teorell-Meyer-Slevers model for sodium chloride, We carried out various permeation experiments using four types of neutral solutes: ethanol, 2-propanol, t-butanol, and glucose, as well as sodium chloride. We analyzed the relationship between the volumetric nux and real rejection, and compared the experimental results with the model calculations. There was good agreement between the experiments and calculations.