Abstract: he operation characteristics of the high temperature gas-cooled reactor pebble-bed module (HTR-PM) are more complicated than that of single-reactor plant due to its multi-modules. A lumped parameter dynamic model of the HTR-PM was developed and was employed to simulate the operation process. The operation simulation results of the power increase show that the steam temperature departs drastically from its allowable range. A simple controller based upon the steam temperature was designed therefore. The simulation results with the controller show that the plant parameters are all well controlled and the results are satisfactorily accepted.