An embodiment of the invention discloses a method and a device for assigning group identify (GID). Non-conflict GID can be assigned for non-AP STA in coverage of multiple BSS (basic service set) network areas, and confliction caused in the process of assigning the GID for the non-AP STA can be reduced. The method includes dividing all the GID into N parts according to quantity, assigning the GID to N BSS which utilize multiuser multiple input and multiple output mode (MU_MIMO) communication, and further, through an access point AP of one BSS network, assigning GID for the terminal non-AP STA in the BSS network according to a preset sequence of the GID assigned for the BSS network, wherein the N BSS networks share a common area, and the N is the natural number larger than 1.