The invention discloses an automatic boiler combustion control system of a circulating fluid bed, which is applied to machine sets for coal-fired power generation, heat supply or combined heat and power generation. The system comprises hardware and control program software, wherein the control program software comprises a fuel control part, an air volume control part and a deslagging control part, and the control program software can automatically and timely control the input quantity of boiler fuel, the oxygen content in the boiler and the boiler deslagging device. The combustion control system is applicable to all sorts of complicated operating conditions, has consistently correct and reliable reaction, advanced and reasonable algorithm design as well as good control effect, is safe and effective, has the capabilities of improving boiler combustion condition, increasing boiler combustion efficiency and reducing unburned carbon in flue dust, leads main steam pressure control to be stable, enhances the capability of tracking the change in load of the boiler and greatly improves the running safety performance, leads main steam temperature control precision to be effectively improved, avoids temperature excursion of an overheater, reduces the danger of steam turbine water slug caused by low-temperature steam, and improves the thermal efficiency and automation control degree of the steam turbine.