Data transmission method, system and transmitting terminal

The embodiment of the invention discloses a method for transmitting data, which comprises the following steps: when a sending end schedules data packets for a receiver again, if the last sent data packet is determined to be discarded when former data packets is scheduled, the maximum value of sending sequence numbers TSN corresponding to the non-discarded data packets before the last data packet is further determined when the former data packets is scheduled, TSN is set for the data packets that are scheduled again, which starts from the number adding 1 to the maximum value. The embodiment ofthe invention also discloses a data transmission system and the sending end, and the sending end comprises a sending end MAC layer processing unit and a sending end RLC layer processing unit. By adopting the method, the system and the sending end disclosed by the embodiment of the invention, the time delay of data transformation can be reduced.