Abstarct: Gas sensors are essential for detecting harmful gases because toxic gases are often flammable, odorless, colorless, invisible, and evaporate quickly. Compared to other materials used for gas sensors, mextal oxide semiconductors have attracted much attention for gas detection due to their low cost, simple design, ease of production, short response time, and extensive detection range. The purpose of this study was to investigate the experimental results of the synthesis of ZnO nanostructures and analyze ethanol gas sensing mechanisms. In the experimental section, we first focused on the synthesis method and study of structural properties, morphology, and optical properties of porous ZnO nanofibers. Then, we studied the factors involved in increasing the sensor performance. The analysis of the XRD pattern in the annealed sample indicated the presence of highly crystallized ZnO nanoparticles. Analysis of the XRD pattern in the sample after annealing indicates the presence of highly crystallized ZnO. Comparison of the two samples after annealing showed that as the annealing temperature increased, the number of plates (002), which is likely to have more oxygen depletion, increases. The FE-SEM images of samples also emphasized the formation of porous ZnO nanoparticles. By increasing the temperature, we also witnessed an increase in the porosity of samples. The results of sensory examination of the samples showed that the sensor response in the presence of different concentrations of ethanol gas and at different operating temperatures for the Z-5 sample has the highest value. The response of Z-3 sample at 〖300〗^(°C) and 800 ppm concentration was 41% and the response of Z-5 sample at the same concentration and temperature was 52%.