The invention provides a denitration reactor, a denitration device and a flue gas denitration method. The denitration reactor comprises a housing, a rotary shaft and partition plates. A flue gas inlet and a reducing gas inlet are formed in the lower portion of the housing, and a gas outlet is formed in the upper portion of the housing; the flue gas inlet and the reducing gas inlet are oppositely formed; the rotary shaft is arranged in the housing along the axial direction of the housing; the partition plates are fixed on the rotary shaft to divide the inner portion of the housing into at least two reaction chambers, each of the reaction chambers is filled with catalyst particles, and the flue gas inlet and the reducing gas inlet are separately communicated with different reaction chambers. By means of the denitration reactor provided by the invention, an adsorption process and a reducing denitration process are separately performed, and the denitration efficiency is enhanced under the circumstance that O2 interferes with a reducing agent. Meanwhile, the catalyst driven by an air flow is in a boiled state, so that the denitration efficiency is further improved. In addition, the catalyst particles can be also replaced and adjusted without halting down, so that escape of flue gas is avoided.