La 0.7 Sr 0.3 FeO 3 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(NO 3 ) 3 Á6H 2 O ? Sr(NO 3 ) 2 ? Fe(NO 3 ) 3 Á 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°C. The gas sensing mechanism is also discussed.