The invention provides a deep-sleep method of embedded system. The method mainly comprises the following processing steps: 1, in the system operating status, judging whether no operation is performed for long time to ensure that if so, the system preservation process is carried out after the hardware operation is ensured to be completed and then the system is closed to enter the deep-sleep mode, or receiving a system-closing signal; 2, starting the system, searching a deep-sleep block after the mapping and initializing of memory; after finding the effective deep-sleep sign, performing system data recovery process; and 3. after successfully recovering the system, performing the initializing of the related hardware, and returning to the state before the deep-sleep mode. By using the method of the invention, after the device is powered down or powered off and powered on again, the device can automatically return to the original interface to greatly reduce the power consumption of the stand-by system and save energy and electrical energy, thus prolonging the service time of the battery and ensuring the service life of the related hardware while largely increasing the startup speed of the system.