The invention a dynamic token working method and a dynamic token working system. The authentication requirements of users are divided into two categories in advance, namely login authentication requirements and signature authentication requirements during signature in the transaction processes (after login); after the dynamic token is activated successfully, the dynamic token generates corresponding login private keys and signature private keys for the two categories of the authentication requirements in advance. Subsequently, when a user has the transaction requirement and needs login or signature authentication, the dynamic token generates a corresponding login answer-back code or a signature answer-back code for the user according to the login private key or the signature private key in combination with a challenge code input by the user at the moment. Obviously, according to the dynamic token working method, different calculation private keys are set for different authentication requirements of the users, and therefore, the private keys of the dynamic token are not easy to break, and the working mechanism and the working flow of the dynamic token are safer; besides, dual authentication during the transactions of the users is realized, the difficulty for lawbreakers to reversely infer the working principle of the dynamic token is improved, and the security of user accounts is guaranteed.