The invention relates to a fuel cell system, which comprises a fuel cell stack and a fuel box. The fuel box is provided with a shell and an air bag, wherein a space is formed in the shell to store fuel required by operation of the fuel cell stack; the shell is also provided with a fuel outlet and an air inlet; the fuel outlet is connected to the fuel cell stack though a pipe; and the air bag is arranged in the shell, and an opening of the air bag is tightly jointed and communicated with the air inlet on the shell.