Xylene poses a risk to the health of humans even in the low concentration range. Therefore, it is crucial to develop some sensing materials, which exhibit high sensitivity, excellent selectivity, and ultra-low detection limits towards xylene. Although most semiconducting metal oxides, including In2O3, show acceptable sensitivity to alcohols and aldehydes, they have difficulty detecting para-xylene effectively, which is a less chemically reactive compound. In this study, a one-step electrospinning process was utilized to introduce both calcium and ruthenium into the In2O3 nanofibers. Calcium was added to increase surface alkalinity, while ruthenium acted as a catalyst for further promoting the sensing activity of In2O3. The results indicate that In2O3 nanofibers doped with 5% calcium and modified with 1% ruthenium gave improved response, selectivity, and decreased operating temperature compared to single modified In2O3, which could be attributed to the dual introduction of calcium and ruthenium, leading to the increased alkalinity, the electrosensitization and chemosensitization, respectively.