An exemplary method for conserving power of a portable communication device includes: supplying voltage by a power supply; distributing voltages to other units of the portable communication device including a communication unit and a backlight unit; the portable communication device entering a normal mode after being powered by one of the voltages; generating digital voltage signals corresponding to the voltage supplied by the power supply; detecting a voltage of the digital voltage signals to obtain a detected voltage; comparing the detected voltage with a predetermined value; and if the detected voltage is equal to or less than the predetermined value, changing from the normal mode to a power conserving mode, and stopping distribution of the voltages to at least one of the communication unit and the backlight unit. Thereby, an operational time of other units of the portable communication device can be prolonged.