Purpose - The purpose of this paper is to synthesize SnO2-ZnO hollow nanofibers, study their sensing properties and introduce an attractive candidate for formaldehyde detection in practice. Design/methodology/approach - Pure and SnO2-ZnO hollow nanofibers were synthesized by electrospinning method and characterized via X-ray diffraction, field-emission scanning electron microscopy and Fourier transform infrared spectroscopy. The formaldehyde-sensing properties were investigated. Findings - The optimum performance was obtained at 260 degrees C by the 14 at.% SnO2-ZnO hollow nanofiber sensor. The sensor could detect formaldehyde down to 0.1 ppm with rapid response-recovery time (4-6 s and 7-9 s, respectively), high sensitivity, good selectivity and stability. The relationship between the sensor's sensitivity and formaldehyde concentration suggests that the adsorbed oxygen species on the sensor's surface is O2-. The prominent sensing properties are attributed to the one dimensional hollow nanofiber structures and the promoting effects of SnO2. Practical implications - The sensor fabricated from 14 at.% SnO2-ZnO fibers exhibits excellent formaldehyde-sensing characteristics. It can be used for formaldehyde detection in practice. Social implications - The electrospinning method is a very simple and convenient method for fabricating hollow nanofibers and the sensing material is of low cost. Originality/value - To the best of the authors' knowledge, studies on formaldehyde sensing of SnO2-ZnO hollow nanofibers have not been reported before.