Objective To investigate the filtration roles of microporous membranes with different pore sizes in the tumor cells with different diameters,and effects on the filtered cells.Methods Three kinds of tumor cells with different cell diameters and same concentrations,including Jurkat,K562 and A549,were filtered by the polycarbonate microporous membranes with different pore sizes such as 1,3,5,8 and 10 μm,respectively,and their filtration rates were determined.The diameters of three kinds of tumor cells before and after filtration,and the fixed K562 cells with formaldehyde,were measured by an optical microscope.The activity of the filtered K562 cells were detected by the trypan blue staining.After the filtered K562 cells were re-cultured,their proliferation activity was analyzed by the growth curve.Results Jurkat,K562 and A549 cells couldn't pass the filter membrane with 1 μm of pore size.The filtration rates of three kinds of tumor cells passing the fliter membranes with 3 μm,5 μm,8 μm and 10 μm of pore sizes increased in turn.The survival rate of K562 cells filtered by 3 μm of pore size of membrane was 92.0％,and the proliferation acticity of re-cultured K562 cells was still strong.The filtration rate of the fixed K562 cells with formaldehyde was significantly decreased,and the average diameter of the filtered cells had no obvious change.Conclusion The living cells are able to pass the membranes with the pore sizes less than their diameters.The living cells passed the filter membranes may still maintain their growth and proliferation activity.However,the fixation of formaldehyde may significantly reduce the number of cells passed the membrane.