Abstract: Micropore filtration of leukocytes is one of the main methods for evaluating leukocyte's deformability. Here a biofluid mechanical model was proposed for three cases: (i) firltration under gravity; (ii)constant pressure filtration; (iii) constant flow rate filtration. In previous models, constant blood cell resistance was assumed. In this paper, when evaluating the filter resistance to leukocytes, not only the effect of the change in the driving pressure but also the difference in the deformability of individual leukocytes are taken into consideration. Moreover, based on Moessmer's experimental results, a probability distribution function.for the transit time of polymorphonuclear cells (PMNs) through the filter is assumed. Finally, numerical curves are obtained for the above three types of filtration and the comparison between the theoretical andexperimental results of PMNs for case (i) turns out to be satisfactory The two parameters in the model. A and B represent leukocytes deformability under low and high pressures respectively.