The invention relates to a monolithic flue gas denitration catalyst with silicon-based ceramic as a carrier and a preparation method thereof, which pertains to the fields of atmospheric pollution treatment technology and pollution-free catalyst materials. The monolithic flue gas denitration catalyst is characterized in that the silicon-based ceramic is taken as a first carrier, active silicon dioxide is taken as a second carrier, a proper amount of one or a plurality of transition metal oxides of Mo, W, Cu, Fe, Zr, La, and the like, is added to CeO2 as the active components. The preparation method adopted is as follows: the silicon-based ceramic is immersed into alumina sol, dried and baked to prepare an active silicon dioxide coating, and then immersed into Ce(NO3)3 solution to prepare an active CeO2 coating. Compared with the prior art, the preparation method of the invention not only improves the mechanical and heat stability of the catalyst carrier, and reduces the load of the active components, but also protects the environment without secondary pollution, enhances the activity of the catalyst, and increases the activity temperature window.