Embodiments of the present disclosure provide a unified authentication method for application in a trunking system, a server and a terminal. The method includes: an application service network element of a server receives a registration request transmitted by a terminal and transmits the registration request to an authorization authentication network element, where the registration request carries a token indicating a unique identity of a user initiating the registration request, and the token is assigned by the authorization authentication network element of the server to the user when the user logs onto the terminal; the authorization authentication network element then performs a token authorization to the user according to the token; and finally the application service network element performs an application service interaction with the terminal if the token authorization is passed.