Artemisia nilagirica (Clarke) Pamp were collected from Theni district. In the present investigation, the leaf extract of Artemisia nilagirica (clarke) pamp was subjected to column chromatographic separation and the fractions were subjected to thin layer chromatography. The Rf value was authenticated to be 0.71 for flavonoids from Artemisia nilagirica. In our work study, petroleum ether, ethyl acetate, methanol and aqueous extracts and standard L. Ascorbic acid of Artemisia nilagirica (Clarke) Pamp have been evaluated for in vitro antioxidant activity at different concentration of 20, 40, 60, 80, 100 respectively. The IC50 value for DPPH inhibition of methanol (81.68 μg/ml), ethyl acetate (69.73 μg/ml), Aqueous (77.37 μg/ml), petroleum ether (65.41 μg/ml) and L Ascorbic acid (85.39 μg/ml) respectively. In LC-MS of the active compound of quercetin gave (M-H)- at M/Z 301. For showing a highest peak and molecular weight to be 302. The results of this study also provide a scientific support to medicinal uses of Artemisia nilagirica in Theni. The In Vitro antioxidant activitites could be accredited to the highest peak of active components identified in Artemisia nilagirica leaves by LC-MS analysis.