A power control system includes a power supply unit, first and second microcontrollers, a transmission line and first and second filters, for transmitting a power management bus (PMB) to a server. The power supply unit provides a power signal, the PMB and a carrier frequency. The first and second microcontrollers respectively perform modulation and demodulation to the PMB according to the carrier frequency, such that the transmission line simultaneously transmits the power signal and the PMB to the server.