The invention discloses a cash-out system and method based on a cryptographic algorithm. The cash-out system comprises an ATM master control unit, an algorithm authentication unit and a cash processing unit. The ATM master control unit receives bank server information and client operation information, processes and encrypts the received information and forwards the information to the algorithm authentication unit. The algorithm authentication unit receives a cryptograph instruction sent by the ATM master control unit, a secret key is used for carrying out decryption and signature verification on the received cryptograph instruction, and the decrypted clear instruction passing verification is forwarded to the cash processing unit. The cash processing unit receives the clear instruction forwarded by the algorithm authentication unit, and an action module is controlled to act to achieve instruction requirements. A cash-out based on the cryptographic algorithm is formed by the algorithm authentication unit and the cash processing unit, a control instruction is transmitted through the cash-out unit and the ATM master control unit in the mode of ciphertexts, the control instruction cannot be directly acquired, an illegal instruction is intercepted, and the problem existing in an existing cash-out system is solved.