A direct-mode communication system having a user direct-mode communication apparatus and a serving direct-mode communication apparatus is provided. The user direct-mode communication apparatus connects to an operating server, and authenticates with the operating server to obtain a user authenticated identification. The serving direct-mode communication apparatus connects to the operating server, and authenticates with the operating server to obtain a serving authenticated identification. The user direct-mode communication apparatus broadcasts a discovery signal based on the user authenticated identification. The serving direct-mode communication apparatus receives the discovery signal after the user direct-mode communication apparatus enters a default serving range, and provides interactive information to the user direct-mode communication apparatus according to the discovery signal and based on the serving authenticated identification.