A series of Fe0.8Mg0.2Oz catalysts for selective catalytic reduction (SCR) of NOx with NH3 were prepared via coprecipitation method with microwave thermal assistant at different calcination temperature. The influence of calcination temperature on the catalytic performance, microstructure properties, surface elements and acidity over Fe(0.8)Mg(0.2)O(z)z-T catalysts was investigated by various characterization methods. Fe0.8Mg0.2Oz catalyst calcined at 400 degrees C showed the highest NOx conversion and excellent N-2 selectivity. More than 90% NOx conversion could be achieved in a wide temperature range of 250-350 degrees C. Fe0.8Mg0.2Oz-400 with large surface area and pore volume obtained a high purity gamma-Fe2O3 crystalline phase with the calcination temperature of 400 degrees C. Meanwhile, Magnesium had strong interaction with gamma-Fe2O3 and existed in either highly dispersed or amorphous phase. Surface oxygen concentration and acidity (mainly Bronsted acid sites in Fe0.8Mg0.2Oz-T catalysts) played an important role in SCR reaction. The results implied that the higher surface area, pore volume, strong interaction, superior surface acidity and redox ability contributed to the excellent SCR catalytic performance of Fe0.8Mg0.2Oz catalyst calcined at 400 degrees C.