A computer program product, apparatus and method for establishing a voice call of a mobile communication system includes: authenticating an origination terminal through a traffic channel by performing call connection between the origination terminal and an origination side network; authenticating a destination terminal through a traffic channel by performing call connection between a termination side network and the destination terminal when the authentication is successful; and establishing a speech path between the origination terminal and the destination terminal when the destination terminal is successfully authenticated. A request and submission of an OTP for authenticating a user of a mobile terminal is possibly performed according to the voice call protocol, whereby the security of the mobile terminal can be strengthened and the strong demand of users with respect to protecting the privacy and information can be satisfied.