The use of medicinal plants is increasing because people believe that they are safe for human consumption. According to the World Health Organization “a medicinal plant” is any plant, which in one or more of its organ contains substances that can be used for the therapeutic purposes or which are precursors for the synthesis of useful drugs. In Africa as well as in Ethiopia plants are usually used as medicinal agents. Roots, leaves and barks are extracted and processed to produce chemical compounds that work for different kinds of diseases and infections. Fromthe common used plants as traditional medicinal plants are Senna species. Senna is a medicinal plant that has been in use over a thousand years. It is a safe andharmless. Senna singueana is one of the varieties of Senna species that is used for different traditional medicinal purposes. The root bark of Senna singueana, one of the most popular herbal products in tropical countries, isused in traditional medicine for treatment of several diseases and ailments. The present study was conducted to investigate the anti-oxidative activities of different solvent extracts of Senna singueana root barks. The results indicated that all extracts have reducing power of DPPH radical scavenging abilities. Methanol and ethyl acetate extract of the root bark extracts have the highest total reducing powerand petroleum ether showed the lowest reducing power. Qualitative phytochemical screening of this part indicated the presence of alkaloids, flavonoids, steroids, terpenoids,saponins and tannins with different concentration. Quantitative analysis of the root bark of Senna singueana for phenolic, flavonoid and total anti-oxidant compounds revealed that the total phenolic content ranged from 20.01 to 273.46 mg/g of dry weight of extracts which expressed as Gallic acid equivalents. The total flavonoid contentvaried from 30.3889 to 240.83 mg/g of dry weight of extracts that expressed as Quercetin equivalents. The total anti-oxidant content using Phosphomolybdate assay varied from 26.178 to 304.15 mg/g, expressed as mg of ascorbic acid equivalent (AAE). Key words:Senna singueana, antioxidant activity, antimicrobial activity, total phenolic content and total flavonoid contents.