Automatic gain control method and automatic gain control device

The invention discloses an automatic gain control method and an automatic gain control device. The automatic gain control method comprises the following steps: detecting the current communication system; selecting a control strategy corresponding to the current communication system according to a pre-stored corresponding relationship between communication systems and control strategies, wherein the control strategies include rapid control and slow control; and carrying out automatic gain control according to the selected control strategy. According to the invention, as the control strategy corresponding to the communication system is pre-stored, and adaptive matching is performed to switch to the corresponding control strategy to carry out automatic gain control after the communication system is determined, automatic gain control can be carried out under a multi-mode system or a mixed-mode system.