A processing system includes random access memory, memories, a main processor, and a microprocessor. The random access memory is configured to store code. The main processor is configured to transfer the code to a first memory in the memories. The microprocessor is configured to set the memories into a self-refresh mode and turn off the main processor in a standby mode. The microprocessor generates a first command based on a predetermined event, in which the main processor is further configured to be activated according to the first command, in order to enable the first memory. The microprocessor executes a standby application according to the code stored in the first memory, in order to confirm whether to operate in the standby mode constantly.