A method for achieving power management for a PDA is disclosed. The PDA contains a CPU for processing data, a microprocessor for supervising power condition of the PDA, and a display module for displaying data and information. The microprocessor and the CPU are used to switch the PDA from OFF mode to SHUTDOWN mode. When the PDA is in OFF mode, the CPU, the microprocessor, and the display are all off, and when the PDA is in SHUTDOWN mode, the CPU and the display module are off while the microprocessor is on. Next, the PDA is switched from SHUTDOWN mode to ON mode. When the PDA is in ON mode, the CPU, the microprocessor, and the display module are on. The PDA can then be switched among SHUTDOWN mode, STANDBY mode, and SCREEN TOGGLE mode for managing the power of the PDA.