The optimal reaction conditions were as the following: loading amount 5%, hydrothermal modification method, WHSV 2 h1, reaction time 10 h, reaction temperature 340 8C, ethanol concentration 20%. The best yield of ethylene was up to 97.8% over Mn-SAPO-34 at the reaction temperature of 340 8C at this optimal reaction conditions. So far we obtained the best yield in dehydration reaction of bio-ethanol compared with other reported results.