The invention discloses a digital signature authentication system based on a third party and an authentication method, belonging to the technical field of communication and comprising a user management center, a user terminal, a user password and a digital signature authentication center. The user terminal performs digital signature to relevant information by utilizing USBKey after receiving a user service request and sends digital signature information to the user password and the digital signature authentication center; the user password and the digital signature authentication center validate the digital signature and then send an instruction generated by information such as the banking account of a user and the like to relevant banks through a special network, and the banks return a processed result to the user password and the digital signature authentication center after checking and processing the account information of the user; the user password and the digital signature authentication center send a service request to the service department and return the service processed result to the user terminal, and the user terminal finishes the service. The invention has the advantages of safety, reliability, high efficiency and easy expansion, thereby being suitable for communities.