Abstract: The hydroxytyrosol(HT) was prepared from oleuropein(OE) in the olive leaves by enzymatic hydrolysis. The qualitative and quantitative determination of OE and HT from the olive leaf extract were analysed by HPLC, and the best enzyme to hydrolyze OE for HT from olive leaf extrct was selected. Moreover, the optimal technology of enzymatic process was obtained by single factor test and orthogonal test. The DPPH radical scavenging effects of HT, OE and olive leaf extract were examined, too. The results showed that hemicellulase was the best enzyme to hydrolyze OE for HT in the same enzymatic activity from 10 enzymes, and the cellulase and β-glucosidase were second. The optimal conditions were temperature 60 ℃, pH value 5.5, enzyme quantity 40 mg and time 6 h. The degradation rate of OE was 85.28 %, and HT content was 6.07 % by the best enzymatic process. Furthermore, HT was obtained by acid- and base-treatment, respectively. Acid hydrolysis performance (7.41 %) was better than enzymatic hydrolysis, and base-treatment result(4.09 %) was the worst. By comparison of the two methods, it was found that enzymatic condition was mild and could reduce the catalyst use, and it is a new hydrolysis method to further develop and utilize. The IC50 of HT was 1.07 mg/L, and the radical scavenging effect was in the order of HT> Vc> OE> BHT> olive leaf extract. Therefore, HT has a good ability of anti-oxidation compound.