The invention discloses an encryption system for RTOS system program mirror image files. The system comprises a maintenance tool packaging module, a terminal unpackaging module and a terminal loadingmodule. The maintenance tool packaging module is used for encrypting, signing, packaging and downloading mirror image files. The terminal unpacking module is used for decrypting, verifying and storingthe encrypted mirror image file sent by the maintenance tool packing module. The terminal loading module is used for decrypting, signing and loading the stored encrypted mirror image file after the device is powered on. Through dual protection of encryption and signature, the terminal avoids leakage of a program mirror image plaintext, the credibility of a program mirror image file is ensured, and the running safety of the terminal is effectively enhanced.