Abstract: Internal model control is a new control strategy based on process mathematical model for controller design. It has the advantages of simple structure, intuitive design, no need for accurate mathematical model, and less on-line adjustment parameters. In order to explore the application of internal model control in the field of reactor control, taking the core power control of molten salt experimental reactor as an example, a linearized model of the primary loop system of molten salt experimental reactor was established. The internal model control technology was adopted and the core power internal model controller was designed by combining particle swarm optimization. Based on MATLAB/Simulink, the primary circuit simulation system of molten salt experimental reactor was established, and the power control of liquid molten salt experimental reactor under step reactivity disturbance was studied. The results show that the internal model controller can control the core power well and realize the fast and stable system.