Abstract: Five different extracts of Mentha canadensis L. through water, ethanol, 70% ethanol, butanol and ethyl acetate were evaluated by tree models of antioxidant activity:1, 1- diphenyl-2- picrylhydrazyl ( DPPH) , 2, 2'- azino -bis ( 3- ethylbenzthiazolne- 6-sulfonic acid ( ABTS) and ferric reducing antioxidant potential assay ( FRAP) . The relationship between the antioxidant activity and the content of total phenolics and total flavonoids was analysed. The results showed that all the extracts had great antioxidant activity and the content of total phenolics had a highly significant correlation with the activity, however, low correlation with the content of total flavonoids.The water extract showed that the highest radical scavenging rate on DPPH and the EC 50 was ( 0.53 ± 0.04) mg /mL. The methanol extract showed the highest radical scavenging rate on ABTS and the EC 50 was ( 1.57 ± 0.03 ) mg /mL. The ethyl acetate extract showed the highest value of FRAP and EC 50 was ( 4.73 ± 0.03) mmol /g.The highest content of total phenolics and total flavonoids came from water extract and methanol extract and the content of them were ( 58.81 ± 3.10) , ( 162.95 ± 1.91) mg /g, respectively.