Magnetic -Fe2O3 catalysts were prepared by microwave-assisted coprecipitation utilizing the direct-titrate and back-titrate precipitation technique with different precipitants, namely, (NH4)(2)CO3, NaOH, Na2CO3, and NH4OH, which were evaluated in the selective catalytic reduction of NOx with NH3. The optimum -Fe2O3 catalyst preparation method was direct titration with NH4OH as the precipitant, which exhibits high deNO(x) efficiency. This direct titration was effective to maintain the proper crystallization degree of -Fe2O3, improve the pore structure, and suppress the formation of -Fe2O3 phase, being advantageous to get tiny and uniform discrete -Fe2O3 particles with high activity in selective catalytic reduction. NH4+-based precipitants in direct titration leads to an increase of the surface O/Fe atom ratio, and more lattice oxygen sites are exposed to the crystal surface.