This study was designed to determine the polyphenolic contents of Eucommia ulmoicles Oliv leaf extracts and evaluate their antioxidant activities in vitro. All the extracts were evaluated for their radical scavenging activity by the DPPH method and their oxidative-retarding efficiency in vegetable oils. It was observed that the highest values were found in 70% MeOH extracts for total phenolic content as gallic acid. A good correlation between antioxidant activity and total phenol content in the extracts was found. The extraction yield, total phenol content and radical scavenging activity were increased and peroxide formation in vegetable oils were decreased with the graded solvent concentration of MeOH. The phenolic compound yield ranged from 2.45 to 11.35% and the total phenol content increased from 34.51 mg/g to 47.68 mg/g. DPPH scavenging activity increased from 56.32% to 90.37% as MeOH concentration increased. Compared to the control (70.45 meq/kg), 70% MeOH fraction with 47.68 mg/g phenolic compounds shows much stronger antioxidant ability (30.12 meq/kg) in vegetable oil system.