The disclosure discloses an identifier assignment method in a Wireless Local Area Network (WLAN), which includes: a group identifier is set for a non-Access Point Station (STA). The method further includes: in a process during which the STA associates or reassociates to an Access Point (AP), a terminal identifier is assigned to the associated or reassociated STA or a terminal identifier and a group identifier are assigned to the associated or reassociated STA. The disclosure also discloses an identifier assignment device in a WLAN for implementing the terminal access method. The terminal identifier is significantly expanded through the setting of the group identifier, so that a unique identifier can be assigned to the STA accessing to the AP without identifier repetition of the STA. Meanwhile, the grouping of the STA also facilitates the scheduling and management of the STA in a group. The disclosure ensures that sufficient STAs can access to the AP and a different identifier can be assigned to each STA.