A data transmission method, system and device

The present invention discloses a data transmission method, system and device for the case where the MBMS-related multiple logical channels are mapped to the same transport channel, to meet the quality requirements of a variety of logical channels transmit data. A data transmission method of the present invention comprises: a network side determines modulation coding set MCS plurality of logical channels are mapped to the plurality of the same transport channel requires, and notifies the correspondence relationship with each MCS to the different logical channels a terminal; the MCS by the network side of the transmission channel to be utilized for the transmission data of the logical channel is mapped onto modulation and coding, and then transmitted to the terminal through the transmission channel.