A data transmission method, comprising: generating a multi-band transmission connection establishment message frame, wherein the multi-band transmission connection establishment message frame is used to request simultaneous transmission of data frames on at least two frequency bands; sending the multi-band transmission connection establishment message frame on the at least two frequency bands; and sending the data frames on the at least two frequency bands, wherein the sending the multi-band transmission connection establishment message frame on the at least two frequency bands comprises: sensing a channel state on the at least two frequency bands; and determining a back-off duration when there is a third channel in a busy state on the at least two frequency bands; and sending the multi-band transmission connection establishment message frame on the at least two frequency bands after waiting for the back-off duration, wherein the determining the back-off duration comprises: determining a corresponding back-off duration for each third channel by using the random back-off mechanism when there are n third channels, where n is an integer greater than 1; and determining a minimum back-off duration among the n back-off durations as the back-off duration. generating a multi-band transmission connection establishment message frame, wherein the multi-band transmission connection establishment message frame is used to request simultaneous transmission of data frames on at least two frequency bands; sending the multi-band transmission connection establishment message frame on the at least two frequency bands; and sending the data frames on the at least two frequency bands, wherein the sending the multi-band transmission connection establishment message frame on the at least two frequency bands comprises: sensing a channel state on the at least two frequency bands; and determining a back-off duration when there is a third channel in a busy state on the at least two frequency bands; and sending the multi-band transmission connection establishment message frame on the at least two frequency bands after waiting for the back-off duration, wherein the determining the back-off duration comprises: determining a corresponding back-off duration for each third channel by using the random back-off mechanism when there are n third channels, where n is an integer greater than 1; and determining a minimum back-off duration among the n back-off durations as the back-off duration. sensing a channel state on the at least two frequency bands; and determining a back-off duration when there is a third channel in a busy state on the at least two frequency bands; and sending the multi-band transmission connection establishment message frame on the at least two frequency bands after waiting for the back-off duration, wherein the determining the back-off duration comprises: determining a corresponding back-off duration for each third channel by using the random back-off mechanism when there are n third channels, where n is an integer greater than 1; and determining a minimum back-off duration among the n back-off durations as the back-off duration. determining a corresponding back-off duration for each third channel by using the random back-off mechanism when there are n third channels, where n is an integer greater than 1; and determining a minimum back-off duration among the n back-off durations as the back-off duration.