Porous ZnFe₂O₄spherical structures built from nanoparticles were successfully synthesized by annealing the precursor, which was synthesized via a simple template-free solvothermal route with ethanol/ethylene glycol (EG) binary solvents. Various techniques were employed for the characterization of the structure and morphology of as-obtained products. The results revealed that the samples were composed of large amounts of porous ZnFe₂O₄nanospheres with an average diameter around 230 nm, which were constructed by plenty of nano-sized primary particles. Moreover, gas sensor based on the as-prepared samples was fabricated and its sensing performances were investigated. It was revealed that the as-fabricated sensor device exhibited excellent selectivity toward acetone at the operating temperature 200℃and had a response of about 12-30 ppm acetone, which was about 2.5 times higher than that of sensor based on ZnFe₂O₄nanoparticles. The enhancement in gas sensing properties of porous ZnFe₂O₄nanospheres was attributed to their unique structures.