In this study, a model equation was derived for a submerged, hollow-fiber microfiltration (MF) membrane under constant flux. The validity of model equation was examined in two aspects: different feed water concentration and membrane pore size. When the concentration of starch solution (feed water) was varied from 1.5 to 9.0 g/L, the model equation predicted transmembrane pressure (TMP) variation at the precision of 99% within that range of concentration. In the cases of a different nominal membrane pore size (0.1 and 0.4 mum), it was capable of predicting TMP variation in a good manner. From experimental TMP data, it was ascertained that different pore sizes of membrane hardly affected filtration time. At the same time, TMP, flux, and total resistance distributions along the membrane length, which cannot be measured directly, could be calculated using the model equation.