A system-on-chip (SoC) and a booting method thereof are disclosed. The SoC is coupled to an external memory and includes a read only memory (ROM) and a processor. The ROM stores a first firmware image. The processor is coupled to the ROM. The processor reads the first firmware image from the ROM and verifies the state of the first firmware image. If the first firmware image is damaged, the processor reads a second firmware image from the external memory and verifies whether the second firmware image is legal. If the verification of the second firmware image succeeds, the processor reads and executes the second firmware image to perform a booting process.