A boot method for an embedded system is provided. The embedded system includes two mainboards each provided with a baseboard management controller (BMC), a non-volatile memory unit and a network adapter. When the embedded system is turned on, each of the BMCs performs a boot procedure, and then loads an operating system (OS) image file from a corresponding non-volatile memory unit to execute an operating system. When one BMC fails to load the OS image file or to execute the operating system, the BMC causes the corresponding network adapter to communicate with the other network adapter to acquire the OS image file from, the non-volatile memory unit on the other mainboard, so as to replace the OS image file in the corresponding non-volatile memory unit, and directly loads the OS image thus acquired to execute the operating system.