Abstract: Targeting the urban rail transit signaling system that adopts domestic cryptographic technology, a restoring method of signaling system communication when domestic encryption security chip fails is proposed. The signaling system communication restoring process during encryption failure is expounded, and the signal system performance that adopts this method is verified through test and calculation. Without affecting the existing architecture and function safety level of the signal system, this method is capable of restoring encrypted communication to decrypted communication with bypass function and it will alarm in time, which increases applicability and maintainability of the signaling system.