Different kind of biochemical test (Antioxidant ability assays, Total phenol content (TPC), Total flavonoid content (TFC), Ferric reducing antioxidant power (FRAP) assay, Reducing power assay, DPPH free radical scavenging assay, Superoxide anion radical scavenging activity, Hydrogen peroxide scavenging assay, Nitric oxide radical scavenging assay and 2, 2′-azino-bis (3 ethylbenzothiazoline-6-sulfonic acid (ABTS) were exercised to evaluate antioxidant activity of rosemary leaves extract (RE). The result showed that RE exhibit high Antioxidant ability assays (254.18±11.82 μg ascorbic acid), TPC (136.66±7.41 mg of gallic acid (GAE)/g), TFC (37.13±6.04 mg rutin/g), FRAP ranging from 32.17±1.12 to 1.28±1.56 μm Fe (II)/g, Reducing power assay was found from 33.09±0.09 to 6.42±0.05 mg AscAE/g and IC50 value of RE for DPPH, Superoxide anion radical scavenging activity, Hydrogen peroxide scavenging assay, Nitric oxide radical scavenging assay and ABTS was found 40.76±2.81, 31.62±1.43, 47.37±2.30, 70.48±2.13 and 70±4.67 respectively. It can be concluded that rosemary leaves could be use as antioxidants in food industry to overcome the problem of lipid oxidation and rancidity.