This study investigated a low-temperature methane sensor operating under UV excitation. ZnO microspheres assembled with nanosheets at different levels were prepared by adjusting the solvent dosage, and the influence of solvent dosage on the gas sensing performance of the sensor was examined. The results demonstrated that when 10 mL of alcohol solvent was used, the prepared ZnO microspheres consisted of nanosheets with large pore structures, exhibiting the highest specific surface area (53.057 m2 g−1) and the highest relative percentage of oxygen vacancies (40.64%). These characteristics had a positive effect on enhancing the gas-sensing performance of the ZnO sensor. Under UV irradiation, the sensor exhibited a response value of 4.642 for 1000 ppm methane at 60 °C, with a response time (τres) of 32 s and a recovery time (τrec) of 81 s. Meanwhile, the sensor has excellent repeatability and selectivity, which will be endowed with promising application prospects in CH4 detection. [ABSTRACT FROM AUTHOR]