In order to solve the problem that the fuel grain size in the sintering process cannot be detected online and the hysteresis quality of manual detection is large, a fuel grain size measurement system based on robot and multi-layer intelligent screening machine is proposed. The sampling device is used by the system at first to obtain fuel samples, then the microwave device is used to dry the fuel, and the multi-layer intelligent screening machine is used to screen the dried fuel, and finally, the integrated weighing device is used to obtain the fuel quality of each grain size after screening, so as to calculate the fuel grain size distribution value. The system is put into practical use in a steel mill, and the operation results show that its detection error is less than 5%, which could completely replace manual detection. The key technologies involved in the system, such as fixed mass division technology, microwave rapid drying technology and multi-layer intelligent screening technology, are focused on in order to provide reference and guidance for the improvement and large-scale application of the system.