Self-test system for PCIe and method thereof

A self-test system for PCIe and a method thereof are provided. First circuit interconnect card and second circuit interconnect card are inserted into CEM slots respectively. First circuit interconnect card and second circuit interconnect card electrically connected to each other through FFC interface. Differential signal is generated by CPU to provide to first circuit interconnect card/second circuit interconnect card. Differential signal is provided to other second circuit interconnect card/first circuit interconnect card through FFC interface from first circuit interconnect card/second circuit interconnect card. Differential signal is provided to CPU from other second circuit interconnect card/first circuit interconnect card. Therefore, the efficiency of differential signal of PCIe self-test through circuit interconnect card may be achieved.