A power management method and apparatus, and a power supply system are provided. The method includes: obtaining a power demand value of each module and a rated output power of each power supply unit (PSU) in a communication equipment; calculating the obtained power demand value of each module to acquire a total power demand value of the modules; and adjusting, according to the calculated total power demand value of the modules and the obtained rated output power of each PSU, the current number of the PSUs actually turned on in the communication equipment.