A facile method to prepare microfiltration membrane was proposed in this study. The method involved the interfacial polymerization of 1,6-hexamethylene diamine and adipoyl chloride to form polyamide (nylon 6,6) on the polyacrylonitrile (PAN) electrospun nanofibrous (ENF) membranes as the scaffold. The effects of process parameters, such as monomer concentrations, monomer coating sequence, reaction time and number of reaction cycles, on the amount of polyamide that formed were investigated. It was found that polyamide that formed by interfacial polymerization existed not only on the surface but also in the interior of the ENF membranes. A mechanism was proposed to explain the phenomenon. The pore sizes of the formed polyamide/PAN ENF membranes, ranging from 0.13 to 4.88 mu m, can be controlled by the number of reaction cycles. These polyamide/PAN ENF membranes also exhibited enhanced tensile strength. POLYM. ENG. SCI., 54:430-437, 2014. (c) 2013 Society of Plastics Engineers