1D Co3O4/alpha-Fe2O3 core-shell nanofibers were successfully fabricated by a facile and template-free coaxial electrospinning method, and developed for acetone gas detection. Morphology and component characterizations confirm that the as-prepared 1D heterostructures possess a well-defined core-shell structure with Co3O4 in the core and alpha-Fe2O3 in the shell. The unique 1D core-shell nanostructures, heterojunction effect at the Co3O4/alpha-Fe2O3 interfaces and the catalysis of Co3O4 endow the Co3O4/alpha-Fe2O3 core-shell nanofiber-based sensor with an enhanced gas sensing performance in terms of good sensing selectivity, high sensitivity (11.7), rapid response/recovery times (2 s/20 s) and better reproducibility for acetone gas. The gas sensing mechanism is proposed in detail. Overall, the 1D Co3O4/alpha-Fe2O3 core-shell heterostructure nanofibers synthesized through coaxial electrospinning make a promising and effective acetone sensor.