Plants are rich sources of natural antioxidants that increase the antioxidant power of plasma and reduce the risk of diseases such as cancer, cardiovascular disease and stroke. Because of the toxic and nutritional side effects of synthetic antioxidants, the need for natural antioxidants from plant sources with less toxicity and more efficacy is a serious demand. Haussknechtia elymatica a member of the Apiaceae family was studied for its antioxidant property. The reducing power of ethanolic extract of Haussknechtia elymatica leaf was determined in the reaction mixture containing different concentrations of extracts at 700 nm. Ascorbic acid was used as positive control. The absorbance of extract with concentration of 25 and 800 mg/ml were 0.043 and 0.197, respectively. It was shown that ethanolic extract of Haussknechtia elymatica leaf has an acceptable amount of reducing power compared with ascorbic acid and increased with increasing the concentration of extract. In conclusion, Haussknechtia elymatica has higher reducing power compared with plants of the same family and it can be used as a suitable plant species for therapeutic purposes.