A method and apparatus for data transmission. In the method, a target alert sequence is transmitted to a network access device by using a first uplink grant-free transmission resource corresponding to the target alert sequence. The target alert sequence is configured to notify the network access device that the terminal requests to use the first uplink grant-free transmission resource to transmit uplink data. The uplink data is transmitted by using a transmission resource different from the first uplink grant-free transmission resource, when receiving a collision indication fed back by the network access device in response to the target alert sequence.