The similarity between three models by applying experimental data of NaCl solution per-meation of composite and asymmetric membrane to the membrane transport models and the separation characteristics of each membrane was studied. The plot of rejection coefficient (R) vs. total volume flux(J_v) showed that the experimental data were in accordance with the linear and nonlinear model below the NaCl solution concentration of 15000mg/l. The reflection coefficients of the composite and asymmetric membrane showed Spigler-Kedem nonlinear model to have more validity compared with the linear model. In case, the exponential term in nonlinear model is very small as to be neglected, the nonlinear model is converted into the solution-diffusion model using the Taylor-series. The compo-site membrane showed better rejection rates as high as 6%(2.45MPa) to 34%(0.98MPa) than those of asymmetric membrane(SEPA-97) below the NaCl solution concentration of 10000mg/l. among the composite membranes used in the experiment, FT-30 and SU-700 composite membranes gave the best performance in respect to the permeation flux and selectivity.