A data transmission method is provided. The method include, when the new data needs to be transmitted, starting from a first available transmission opportunity from among available transmission opportunities, attempting, in each available transmission opportunity of the available transmission opportunities, to acquire a protocol data unit generated by a media access control layer according to the new data; and when the protocol data unit is acquired, instructing, according to the number of times, a cycle period and a start time, an HARQ process to transmit the protocol data unit to the base station in each retransmission opportunity starting from the available transmission opportunity corresponding to the acquisition of the protocol data unit.