A data transmission method, comprising: receiving, by a third site, a first transmit frame transmitted by a first site to a second site, and acquiring a transmission end moment of the first transmit frame; transmitting, by the third site, a second transmit frame to a fourth site, and instructing the fourth site to delay returning a response frame; and receiving, by the third site after at least one preset time length after transmission of the second transmit frame ends, the response frame transmitted by the fourth site; wherein the third site is within a coverage area of the first site, and the second site is outside a coverage area of the third site; a transmission end moment of the second transmit frame is not later than the transmission end moment of the first transmit frame, and the preset time length is greater than or equal to a difference between the transmission end moment of the first transmit frame and the transmission end moment of the second transmit frame; characterised in that the acquiring, by a third site, a transmission end moment of the first transmit frame comprises the step of: obtaining, by the third site, the transmission end moment of the first transmit frame by parsing frame header information of the first transmit frame; wherein the step of obtaining the transmission end moment of the first transmit frame comprises obtaining duration of the first transmit frame by using a frame length and modulation and coding scheme information that are in the frame header, and obtaining the transmission end moment of the first transmit frame according to the duration of the first transmit frame and a current moment or a transmission start moment of the first transmit frame. receiving, by a third site, a first transmit frame transmitted by a first site to a second site, and acquiring a transmission end moment of the first transmit frame; transmitting, by the third site, a second transmit frame to a fourth site, and instructing the fourth site to delay returning a response frame; and receiving, by the third site after at least one preset time length after transmission of the second transmit frame ends, the response frame transmitted by the fourth site; wherein the third site is within a coverage area of the first site, and the second site is outside a coverage area of the third site; a transmission end moment of the second transmit frame is not later than the transmission end moment of the first transmit frame, and the preset time length is greater than or equal to a difference between the transmission end moment of the first transmit frame and the transmission end moment of the second transmit frame; obtaining, by the third site, the transmission end moment of the first transmit frame by parsing frame header information of the first transmit frame; wherein the step of obtaining the transmission end moment of the first transmit frame comprises obtaining duration of the first transmit frame by using a frame length and modulation and coding scheme information that are in the frame header, and obtaining the transmission end moment of the first transmit frame according to the duration of the first transmit frame and a current moment or a transmission start moment of the first transmit frame. <EOS>