We describe a facile approach to preparing polymer nanofibers with porous structures by wet-spinning process using a simple double tubular microfluidic device.The method is based on preparation of oil-in-water(O/W)jetting stream,followed by solvent diffusion and internal phase separation.1 Organic solution containing polystyrene(PS),tetrahydrofuran(THF)and perfluorooctylbromide(PFOB)was used as a core solution.2 Aqueous solution containing Tween80 was used as an outer solution.These solutions were pumped into the microfluidic device to form jetting stream.After the jetting stream generation,the organic solvent that was miscible with water subsequently diffused into the outer solution,which induced polymer precipitation and internal phase separation between polymer-rich phase and the non-solvent,and finally lead to formation of polymer nanofibers with internal porous structures.