Abstract: The present invention relates to a method and controlling apparatus for controlling AGC unit. The method provided by the present invention first starts to receive a packet. After starting to receive a packet, an average envelope level of a received symbol in the packet is calculated, and a gain of the AGC unit is adjusted for a first time period by looking up the average envelope level in a table to obtain a first adjustment value. After the first time period is past, the method calculates the average envelope level and adjusting the gain of the AGC unit for a second time period by looking up the average envelope level in the table to obtain a second adjustment value. Moreover, the average envelope level is calculated every time after a first duration is past in the first time period, and is calculated every time after a second duration is past in the second time period, and the first duration is different from the second duration.