An ultraviolet-assisted electrospinning (UVAES) procedure was performed using in situ photopolymerization during the electrospinning process to enhance the solvent resistance of polyimide (PI) ultrafine fibrous membranes (UFMs). The resultant PI UFMs were fabricated via solution electrospinning using photosensitive poly(amic acid ester) (PSPAE) modified with unsaturated double bond side chains as the main fiber-forming agent, diethylene glycol diacrylate as the crosslinker, and titanocene as the photoinitiator. The precursor PSPAE UFMs were prepared via both of normal electrospinning and UVAES procedures and then were converted to PI using thermal imidization at 350 degrees C in a nitrogen imidization. The physical and chemical properties of the obtained PI UFMs were subsequently studied. The fibers exposed to ultraviolet irradiation possessed a smooth surface morphology and maintained their fibrous structure after thermal imidization at elevated temperature as high as 350 degrees C in nitrogen, whereas the crosslink-free PSPAE fibers lost their fibrous structure after heating. Furthermore, as well as providing enhanced thermal decomposition stability, the introduction of a crosslinked structure via ultraviolet irradiation also protected the molecular chains from organic solvents, resulting in excellent solvent resistance of the PI UFMs.