A method for adjusting a signal delivery bandwidth is provided. The method includes the following steps: A media gateway (MG) receives a command request carrying signal delivery bandwidth adjusting information, and the MG adjusts the signal delivery bandwidth according to the signal delivery bandwidth adjusting information. An MG and a media gateway controller (MGC) are also provided. By extending the media gateway control protocol (H.248 or MGCP), the delivery bandwidth adjusting information of a signal is transferred while the signal is transferred, the signal is adjusted according to the signal delivery bandwidth adjusting information, a signal and/or signal list corresponding to the signal delivery bandwidth adjusting information is transferred simultaneously, and the executing process of the signal remains uninterrupted.