Effect of air temperature (50-80^oC) on antioxidant activity, total polyphenol, total flavonoid and quercetin content during drying of purple shallot was studied. Shallot slices with the thickness of 2 mm and pre-treated with 150 mg/L sodium metabisulphite for 2 minutes were used for the drying experiments. The results showed that there were significant differences in the content of bioactive compounds of dried shallot powder that were processed at different conditions (P < 0.05). Total polyphenol, flavonoid and quercetin content increased as air-drying temperature increased (P < 0.05). The radical scavenging activity showed higher antioxidant activity at high temperatures (70 and 80°C) than at low temperatures (50 and 60°C) (P < 0.05). In addition, four commonly used mathematical models were evaluated with the experimental data. The Wang and Singh model was found to give better predictions than the others (R² > 0.9).