The capability to perform fast load changes has been an important issue due to the increasing commercialization of the power market. In the traditional boiler control system, the feedback signals come from the variations of the steam pressure and the steam flow, which leads to a large time delay. Therefore, a new method for the boiler control system based on radiation intensity for improving the load-following capacity of a coal-fired power plant has been developed in this paper. The system is implemented by adding the radiation intensity of the flame to the existing boiler control system as a complement. The radiation intensity obtained by the sensor can directly reflect the input heat in the boiler, with a faster response and higher sensitivity. Field tests on a 300 MW coal-fired power plant reveal that the improved boiler control system increases the load-following capacity. At the same time, the steam pressure variations are smaller as compared with those of the existing control system.