Provided are a method for automatically entering into a secure communication mode that can perform secured voice communication between a transmission terminal and a reception terminal without changing or pre-setting a conventional wireless mobile communication system by forming part of a voice signal as a token for attempting secured voice communication, and a computer-readable recording medium for recording a program that implements the method. The method of the present research includes the steps of: a) generating a token based on a data having the lowest frequency of generation among the voice data outputted from a vocoder of the wireless communication terminal; b) at a transmission terminal receiving a request for a secure communication from a user and transmitting the token to a reception terminal; and c) at the transmission terminal entering into a secure communication mode based on an acknowledge token transmitted from the reception terminal, and performing secure communication with the reception terminal.