The present invention discloses an authentication method and a key device and relates to the information security field. The authentication method comprises initiating user authentication, generating a dynamic code and then a first verification code on the basis of the dynamic code, and outputting the dynamic code, by a key device; and receiving a second verification code entered by a user via a host, and collating the second verification code with the first verification code, by the key device, and if a match is found, the user access is authorized to the key device; otherwise, the user access is prohibited. The key device comprises a trigger module, a generator module, an output module, a communication module, a collator module, a controller module and a security module. According to the present invention, better security is achieved by reducing the possibility of sensitive information disclosure and misuse in case of password theft for the key device.