The purpose of this study is to clarify perstraction(permeation-extraction) factors and to analyze separation mechanism in perstraction using hollow fiber modules. The analytical solution on the concentration profiles in hollow fiber modules has been obtained. Also, using this solution, separation mechanism was analyzed by comparing the mass transfer rate changes according to the changes in perstraction factors such as the properties of hollow fibers, distribution coefficient, potting density, and the thickness, porosity and tortuosity of the hollow fibers. The analyses based on concentration profiles show that the mass transfer rate depends mainly on the solute diffusion in the membrane phase, and it has maximum values when the ration of diameter to pitch is between 0.8-0.9 while hydrophilic membrane shows faster mass transfer rates in the system with the distribution coefficient less than 1, hydrophobic membrane shows faster mass transfer rates when the distribution coefficient is above 1.