A method by which a station (STA) transmits a frame including a buffer state report (BSR) in a wireless LAN (WLAN) system, according to one embodiment of the present invention, comprises the steps of: configuring the BSR of the STA to a first control sub-field among one or more control sub-fields aggregated in an aggregated-control (A-control) field; and transmitting the A-control field through a high throughput (HT) control filed included in a MAC header of the frame, wherein the first control sub-field for the BSR is configured as a short BSR when a second control sub-field in the A-control field includes uplink power headroom information of the STA.