A process for producing a cement clinker comprises (a) preheating a raw meal, (b) deacidifying to at least 95% at above 850≦̸C in the system with a fluidized bed reactor, cyclone seperator and recycling duct, (c) clinkering in a rotary klin, and (d) cooling the clinker. At least 65% of total fuel required for calcining and clinkering is fed to the deacidifying reactor and at least 10% to the clinkering reactor. The process gives the cement of a high uniform quality.