A mathematical model for the simulation of ultrafiltration process has been developed in this study. Ultrafiltration tests were carried out on an aqueous solution of lignosulphonate - a natural polymer - employing a pilot-scale ultrafiltration configuration that accommodates spiral wound membranes. The developed model consists of equations simulating mass transport phenomena across membrane surface involving the transport parameters of ultrafiltration process - solvent membrane permeability (L-p), solute membrane permeability (L-s), diffusivity coefficient of solute over boundary layer thickness (D-s/delta) and solute reflection coefficient (sigma). The knowledge of the model parameters facilitates the prediction of membrane performance and its characterization. The dependence of model parameters on operating conditions - operating pressure (Deltap), feed flow rate (Q(f)), feed concentration (X-f) - was also investigated. The experimental data points of pilot-scale tests were correlated in order to calculate the model parameters, and the prediction results were found to be in good agreement with the experimental data.