The invention discloses a registration-free access control and smart lock registration and unlocking method, device and system. The method comprises the steps that S1, a mobile smart device obtains a two-dimensional bar code in a first display screen of a registration device; S2, the two-dimensional bar code is sent to a server; S3, the server receives the two-dimensional bar code, carries out networking query and verification on real name information registered by a mobile smart device user, generates a ciphertext two-dimensional bar code instruction after the query and verification are successful and passes back the ciphertext two-dimensional bar code instruction to the mobile smart device, and the server stores operation time, verification content and result; S4, the mobile smart device displays the received ciphertext two-dimensional bar code in a second display screen;S5, the registration device identifies the ciphertext two-dimensional bar code; and S6, the registration device decrypts the ciphertext two-dimensional bar code, if the decryption is successful, registration verification is finished, and if the decryption is unsuccessful, the verification is terminated and prompt is sent. According to the method provided by the invention, the privacy of a visitor is protected through network verification.