The porous alumina catalysts with different acidity were prepared and tested for dehydrofluorination of 1,1,1,2-tetrafluoroethane to synthesize trifluoroethylene. The XRD, BET, SEM, NH3-TPD and py-IR techniques were used to characterize the alumina catalysts with different calcination temperatures. The porous theta-Al2O3 showed the excellent catalytic performance, with 35.1 % conversion and the selectivity to trifluoroethylene of 99.0 %. The active sites of catalysts for formation of trifluoroethylene are appropriate weak Lewis acid sites, and the strong Lewis acid sites may result in its rapid deactivation, due to the coke or polymerization of trifluoroethylene. Dehydrofluorination of 1,1,1,2-tetrafluoroethane (CF3CFH2) is a promising route to synthesize trifluoroethylene over theta-Al2O3, the conversion is 35.1 % and the selectivity to trifluoroethylene is 99 % at 450 A degrees C. It was suggested that appropriate number of weak Lewis acid sites was beneficial to the catalysis for dehydrofluorination of CF3CFH2, the weak Lewis acid sites as the active sites of synthesis of trifluoroethylene. On the other hand, the strong Lewis acid sites easily result in deactivation of catalysts derived from the coke or polymerization of trifluoroethylene.