Abstract: In order to study the value of molten salt reactor system in commercial application and analyze whether it can meet the changing demand of power grid load and the ability of safe operation, the 1 GWt pebble-bed fluoride salt-cooled high temperature reactor (PB-FHR) was taken as the research object. The performance of the control system under the condition of changing the parameters of typical load following conditions was simulated and analyzed. The simulation model of thermal hydraulic system and power control system of FHR was established with RELAP5/MOD4.0 program, implanted with the properties of molten salt and calculation formulas. The performance of the control system under the condition of changing parameters of typical load following conditions was simulated and analyzed. Results from simulations show that the FHR has a good load following ability. Under the designed control logic, the reactor power can respond to the load change rapidly with low power overshoot and temperature overshoot, and the operation parameters of the reactor are always within a reasonable operating range.