Abstract: There is provided a method of monitoring a firing condition in a cement kiln, by measuring an intensity of spectrum of a radiation which radiation is emitted from a clinker being fired in a cement kiln, and processing the intensity of the spectrum to produce a parameter for monitoring the condition in the kiln, by correcting the intensity profile of the spectrum by interpolating a profile (range) which is deformed by the absorption with alkali atom(s) in an atmosphere of the kiln. Further, the absorption intensity of the spectrum at a sodium absorption wavelength and potassium absorption wavelength should be continuously measured and corrected by interpolating so as to produce a parameter for monitoring.