The present disclosure illustrates a communication establishing method. The method includes following steps. A communication service program is executed on the mobile device to transmit an identification code to a cloud server. A toll-free number is determined and a communication number corresponding to the identification code is inquired from a lookup table. A control command is transmitted from the cloud server to the mobile device. The mobile device is controlled by the control command to dial a call request containing the toll-free number to a dial-up device. The dial-up device transmits a search request to the cloud server and the cloud server then return the communication number respected to the toll-free number to the dial-up device. Finally, the dial-up device automatic transfers the call request to the communication terminal, so as to establish a communication connection between the mobile device and a communication terminal. |