A boiler load control system and control method for a biomass boiler. The boiler load control system comprises a feeding device as well as a boiler connected to the feeding device, a main water supply pipeline, and a main steam pipeline; the system further comprises a boiler load controller, a reclaimer rotating speed calculation device, and a rotating speed control device which are connected in sequence; the main water supply pipeline and the main steam pipeline are each provided with a sensor; the boiler load controller is used for calculating a rotating speed coefficient for a reclaimer and sending same to the reclaimer rotating speed calculation device; the reclaimer rotating speed calculation device is used for calculating a fuel load instruction reference value and a fuel load set value, and sending the fuel load set value to the rotating speed control device; the rotating speed control device is used for controlling a reclaiming speed of the reclaimer. According to the system and method, the amount of fuel entering a boiler can be automatically adjusted, the boiler load keeps consistent with a boiler load set value in real time, the fluctuation of the boiler load and main steam parameters are eliminated so that the boiler load and main steam parameters maintain stable, the burn-off rate of the fuel can also be increased, and the boiler efficiency is improved.