An association establishment method, comprising: sending, by an access point, AP, a trigger frame, wherein the trigger frame is used to trigger an unassociated station, STA, to perform uplink data transmission and indicate one or more available subchannels for random accessing of the triggered unassociated STA; receiving, by the AP, an association request message sent by an unassociated STA, on an available subchannel of the one or more available subchannels; sending, by the AP, a multi-user block acknowledgement frame, wherein the multi-user block acknowledgement frame includes association acknowledgement information, the association acknowledgement information includes a traffic identifier information subfield, and the traffic identifier information subfield includes a dummy association identifier, and the dummy association identifier indicates that the association acknowledgement information is the acknowledgement information of the association request message; and wherein the association acknowledgement information includes a media access control, MAC, address of the unassociated STA sending the association request message; sending, by the AP, an association response message to the unassociated STA sending the association request message, the association response message carries a first association identifier, AID, wherein the first AID is allocated by the AP to the unassociated STA sending the association request message and used to identify the unassociated STA sending the association request message, wherein the association response message indicates that an association between the unassociated STA sending the association request message and the AP is successfully established. sending, by an access point, AP, a trigger frame, wherein the trigger frame is used to trigger an unassociated station, STA, to perform uplink data transmission and indicate one or more available subchannels for random accessing of the triggered unassociated STA; receiving, by the AP, an association request message sent by an unassociated STA, on an available subchannel of the one or more available subchannels; sending, by the AP, a multi-user block acknowledgement frame, wherein the multi-user block acknowledgement frame includes association acknowledgement information, the association acknowledgement information includes a traffic identifier information subfield, and the traffic identifier information subfield includes a dummy association identifier, and the dummy association identifier indicates that the association acknowledgement information is the acknowledgement information of the association request message; and wherein the association acknowledgement information includes a media access control, MAC, address of the unassociated STA sending the association request message; sending, by the AP, an association response message to the unassociated STA sending the association request message, the association response message carries a first association identifier, AID, wherein the first AID is allocated by the AP to the unassociated STA sending the association request message and used to identify the unassociated STA sending the association request message, wherein the association response message indicates that an association between the unassociated STA sending the association request message and the AP is successfully established.