An antimicrobial nanofibrous membrane for nonpressure driven filtration is reported. m-Aramid as an N-halamine precursor was dissolved in N,N-dimethylacetamide (DMAc), and the m-aramid nanofibrous membrane was formed using an electro-spinning process. The morphology of the m-aramid membrane was analyzed by scanning electron microscopy (SEM), and the mean pore size, pore size distribution and liquid permeability of the m-aramid membrane were determined using a capillary flow porometer. The antimicrobial efficacy of the m-aramid membrane was performed by nonpressure driven filtration. The chlorinated m-aramid membrane showed excellent antimicrobial activity against Escherichia coil and Staphylococcus aureus. The chlorine lost after filtration could be regained upon rechlorination.