In boiler combustion processes, the goals of the operation are to keep the combustor in the optimal condition and alleviate instabilities and their severe consequences. However, control systems based on the oxygen content usually have responses with certain delay. Most flames are turbulent and are affected by several unmeasured disturbances and continuous variation due to several types of fuels burned simultaneously. In this work, cascade control based on flame images, and oxygen is developed to prevent fast disturbances. One loop controls the feature of the flame image by correcting feed disturbance and throughput changes. The other loop controls the outlet oxygen content by eliminating the disturbance, which cannot be identified in the inner control loop. The designable performance bound and the corresponding optimal parameters of the PID controller structure computed from the closed loop operating data are also proposed. Finally, the proposed method is applied to a pilot scale experiment to evaluate the performance of the controller structure and to demonstrate its effectiveness in obtaining higher quality of the boiler combustion control system.