Embodiments of the present disclosure provide a data transmission method and a terminal. The method includes mapping, by the terminal, a first-stage sidelink control information (SCI) onto a physical sidelink control channel (PSCCH); and transmitting, by the terminal, the PSCCH and associated physical sidelink shared channel (PSSCH). The first-stage SCI includes an indication information of a second-stage SCI for the associated PSSCH transmission that is mapped onto the associated PSSCH.