A data transmission method, device and system to improve reliability of a data link. When the sender side detects erroneous data, the erroneous data is discarded and a data retransmission request is sent to the sender side to ensure correctness of received data and improve reliability of the data link; and, when the sender side detects the erroneous data and a bit error rate is greater than a preset bit error rate threshold, the data link gets into auto recovery, and data transmission is resumed after the recovery succeeds, thereby avoiding an excessively high bit error rate, preventing an excessively high probability of omitted checks (the higher the bit error rate is, the higher probability of omitted checks is), and further improving reliability of the data link.