Supported Ag catalyst for ethylene epoxidation was prepared by an impregnation-bioreduction process with Cinnamomum camphora (CC) extract. Influence of bioreduction temperature, concentration of CC extract, silver loading amount, calcination temperature as well as Cs promoter on catalytic performance were thoroughly investigated and the catalysts were characterized. The results showed that the catalyst prepared from bioreduction process exhibited excellent performance for the ethylene epoxidation with O-2. Proper amount of Cs addition could effectively improve the catalytic performance of the catalyst. The optimal catalyst 15Ag/alpha-Al2O3-150Cs gave the EO concentrations of 1.70%, EO selectivity of 87.46% and EO STY of 223.07 g h(-1) L-cat(-1) at 200 degrees C, showing high catalytic stability with no significant decrease in the activity and the selectivity during 50 h. (C) 2015 Elsevier B.V. All rights reserved.