A data transmission apparatus, wherein the apparatus comprises: a processing module (320, 520, 740), configured to obtain configuration information, wherein the configuration information comprises an identifier of at least one logical channel and a transmission mode indication corresponding to each of the at least one logical channel, and the transmission mode indication comprises a first transmission mode indication or a second transmission mode indication, wherein the processing module (320, 520, 740) is configured to establish the at least one logical channel according to the identifier of the logical channel and the corresponding transmission mode indication; and the processing module (320, 520, 740) is configured to obtain a transmission resource according to a transmission mode indication of a logical channel of the at least one logical channel to which device-to-device, D2D, buffered data belongs; a sending module, configured to send the D2D buffered data by using the transmission resource obtained by the processing module (320, 520, 740); and a receiving module, configured to, if the transmission mode indication of the logical channel to which the D2D buffered data belongs is the first transmission mode indication, receive grant information sent by a network device, wherein the grant information is used to indicate the transmission resource, wherein the processing module (320, 520, 740) is configured to, if the transmission mode indication of the logical channel to which the D2D buffered data belongs is the second transmission mode indication, select the transmission resource from a transmission resource pool, wherein the transmission resource pool is a preconfigured transmission resource pool, the transmission resource pool is configured according to broadcast information from a network device (220, 240), or the transmission resource pool is configured according to radio resource control, RRC, dedicated signaling from the network device. a processing module (320, 520, 740), configured to obtain configuration information, wherein the configuration information comprises an identifier of at least one logical channel and a transmission mode indication corresponding to each of the at least one logical channel, and the transmission mode indication comprises a first transmission mode indication or a second transmission mode indication, wherein the processing module (320, 520, 740) is configured to establish the at least one logical channel according to the identifier of the logical channel and the corresponding transmission mode indication; and the processing module (320, 520, 740) is configured to obtain a transmission resource according to a transmission mode indication of a logical channel of the at least one logical channel to which device-to-device, D2D, buffered data belongs; a sending module, configured to send the D2D buffered data by using the transmission resource obtained by the processing module (320, 520, 740); and a receiving module, configured to, if the transmission mode indication of the logical channel to which the D2D buffered data belongs is the first transmission mode indication, receive grant information sent by a network device, wherein the grant information is used to indicate the transmission resource, wherein the processing module (320, 520, 740) is configured to, if the transmission mode indication of the logical channel to which the D2D buffered data belongs is the second transmission mode indication, select the transmission resource from a transmission resource pool, wherein the transmission resource pool is a preconfigured transmission resource pool, the transmission resource pool is configured according to broadcast information from a network device (220, 240), or the transmission resource pool is configured according to radio resource control, RRC, dedicated signaling from the network device.