The invention discloses a denitrifying catalyst using titanium dioxide nano tubes as a carrier. The catalyst mainly comprises the following raw materials: nano TiO2 particles, water, strong alkali and metal salt, wherein the metal salt is one of soluble salts of Ce, Cr or Cu. The invention also discloses a process for preparing the catalyst, namely the preparation process combining water heating and soaking, and in particular, the titanium dioxide nano tubes are prepared by the hydrothermal method, and the metallic components are loaded by the soaking method. The catalyst has the advantages of good denitrifying activity, selectivity and stability and wide application prospect.