Embodiments of the present invention provide a data retransmission method and user equipment, where the method includes: if a network indicates switching from a dual stream transmission mode to a single stream transmission mode, stopping data transmission of one data stream and clearing data in an HARQ process of the stopped data stream; or if a network indicates switching from a single stream transmission mode to a dual stream transmission mode, transmitting retransmission data in an HARQ process of the original data stream without changing the HARQ process number, and transmitting new data in the HARQ process of a new data stream; or using the retransmission data of the original data stream as new data to transmit in the HARQ process of either the original data stream or new data stream.