La0.7Sr0.3FeO3 nanofibers with tunable hollow structures are prepared by a facile single capillary electrospinning and annealing process. The hollow nanofibers are characterized by thermogravimetry and differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen physisorption isotherms. The tunable hollow structures are controlled by adjusting the weight ratio of (La(NO3)(3)center dot 6H(2)O + Sr(NO3)(2) + Fe(NO3)(3)center dot 9H(2)O)/PVP. With the increasing of nitrate/PVP ratio, the diameter and the shell thickness of hollow nanofibers increase. Formaldehyde gas sensing properties are carried out in the concentration range of 0.1-100 ppm at the operating temperature of 240 A degrees C. The gas sensing mechanism is also discussed.