The distributed power supply must change its output according to the surrounding demand. Therefore, in order to use the supercritical CO2 Brayton cycle for a distributed power source, the output of the power generation cycle must be controlled according to the needs of the surroundings. This study focuses on the precooler among the various components of the Brayton cycle of supercritical carbon dioxide and conducts control studies. The design of the controller that fixes the temperature at the outlet of the precooler through the control of the precooler was carried out through the Autonomous Brayton Cycle loop in KAIST. In this study, a control methodology is first developed from a computer simulation code. The experimental data from the Autonomous Brayton Cycle loop, computational simulation is performed and the response to the input of the precooler system is calculated. PID controller is designed by modeling the precooler system and using classic control theory. The suggested controller development process in this study can reduce trial and error in future control development for the supercritical CO2 power cycle.