Total phenol, total flavonoid, reducing powder, electron donating activity, ascorbic acid equivalent antioxidant capacity, antimicrobial and antiproliferative activities of olive leaf extracts were investigated. The contents of total phenol and flavonoid were 257.48 and 92.33 mg in 100 g of olive leaf extract, respectively. The reducing power of the olive leaf extract increased with concentration increasing. Electron donating activity was high in 100 ${mu}g/mL$ treated olive leaf extract as 95.20%. The ascorbic acid equivalent antioxidant capacity of the olive leaf extract was 68.93 mg/g olive leaf extract. The olive leaf extracts showed relatively high antimicrobial activity against Escherichia coli, Salmonella typhimurium, Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas aeruginosa. All of the cancer cell lines including MKN45, HCT116, NCI-H460, and MCF7 have 70-81% as effective growth inhibition.