In this study, the flame spray pyrolysis (FSP) technique was employed to produce WO3 nanoparticles, which were subsequently used as sensing materials for NO2 sensors. To enhance the sensing performance, the effects of flame parameters on the particle properties and sensing performances for 150-1200 ppb NO2 at 125 °C were investigated. The results indicate that WO3 particles with an average crystal size of about 10-20 nm and a standard deviation of about 3-7.5 nm were generated by controlling the precursor and dispersion oxygen flow rate of FSP. Based on the evaluation of NO2 sensing performance, WO3 sensing materials synthesized under the 3/5 flame condition exhibited better sensitivity than sensors made under other flame conditions. In summary, the FSP method and the optimization of flame synthesis parameters could be an effective strategy to prepare the sensing materials with high sensing performance.