Disclosed are a catalyst for removing NOx from flue gas and its preparation. The catalyst comprises vanadium pentoxide, and barium oxide or calcium oxide as active components on a titanium dioxide support and is prepared by uniformly dispersing the metal oxides on the surface of the titanium dioxide support. This support is prepared by sufficiently drying and calcining a metatitanate (TiO(OH)2)-predominating slurry which is obtained from the course of the production of titanium dioxide for pigment from ilmenite. The catalyst exbihits excellent NOx removal activity as well as high durability against SO2, so that it can remove NOx for relatively longer period of time without being deteriorated by the poisoning induced by SO2 and significantly contribute to the prevention of plugging and corrosion of the downstream of a SCR reactor system.