A wireless communication channel operation method and a system of the portable terminal for preventing data loss when switching between different wireless video transmission modes are provided. The method includes transmitting multimedia data to a recipient terminal on a communication channel of a second transmission mode in a wireless video transmission mode, the wireless video transmission mode supporting a first and second transmission modes, receiving buffer state information from the recipient terminal, pausing, when a request for switching to the first transmission mode is detected, transmission of the multimedia data to the recipient terminal, determining the buffer state information, waiting, when the buffer state information indicates presence of multimedia data in a reception buffer of the reception terminal, for completion of playing of the multimedia data in the reception buffer, and switching to the first transmission mode after the multimedia data in the reception buffer is played completely.