A method for initiating a call by a radio, comprising: dividing different channels into more than two zones, wherein different zones comprise different channels, and each zone comprises a control channel and two or more traffic channels; acquiring, based on a zone to which the radio belongs, corresponding resource information of the zone, and determining a control channel and traffic channels available for the radio, wherein the zone to which the radio belongs is determined from more than two zones; staying on the control channel in the case of standby; seeking for an idle traffic channel only in the zone to which the radio belongs by searching the traffic channels as determined when a call is initiated, wherein the call is initiated by a user pressing a PPT button; sending, through the control channel as determined, a call set-up request instruction containing a channel number of the idle traffic channel, so as to notify a called radio to switch to the idle traffic channel for establishing communication; entering into the idle traffic channel to establish communication with the called radio; and determining whether a conversation with the called radio is over or whether a preset call reset time is up when the PPT button for initiating a call is detected to be not used; sending a conversation ending instruction to the called radio or automatically ending the call, releasing, by the caller radio and the called radio, the idle traffic channel, and switching to the control channel to wait for the next call in a case that it is determined that the conversation with the called radio is over or the preset call reset time is up; and occupying, by the caller radio and the called radio, the idle traffic channel to continue the call in a case that it is determined that the conversation with the called radio is not over and the preset call reset time is not up, wherein the caller radio and the called radio continues communicating with each other on the idle traffic channel. dividing different channels into more than two zones, wherein different zones comprise different channels, and each zone comprises a control channel and two or more traffic channels; acquiring, based on a zone to which the radio belongs, corresponding resource information of the zone, and determining a control channel and traffic channels available for the radio, wherein the zone to which the radio belongs is determined from more than two zones; staying on the control channel in the case of standby; seeking for an idle traffic channel only in the zone to which the radio belongs by searching the traffic channels as determined when a call is initiated, wherein the call is initiated by a user pressing a PPT button; sending, through the control channel as determined, a call set-up request instruction containing a channel number of the idle traffic channel, so as to notify a called radio to switch to the idle traffic channel for establishing communication; entering into the idle traffic channel to establish communication with the called radio; and determining whether a conversation with the called radio is over or whether a preset call reset time is up when the PPT button for initiating a call is detected to be not used; sending a conversation ending instruction to the called radio or automatically ending the call, releasing, by the caller radio and the called radio, the idle traffic channel, and switching to the control channel to wait for the next call in a case that it is determined that the conversation with the called radio is over or the preset call reset time is up; and occupying, by the caller radio and the called radio, the idle traffic channel to continue the call in a case that it is determined that the conversation with the called radio is not over and the preset call reset time is not up, wherein the caller radio and the called radio continues communicating with each other on the idle traffic channel. <EOS>