A method for multi-level data transmission includes encoding a data signal to be transmitted into N multi-level signals in accordance with an encoding table, where the data signal is characterized with a stream of binary data segments each of which has a data length of M bits, transmitting simultaneously the N multi-level signals through N data transmission channels, respectively; and decoding the N multi-level signals into the data signal by comparing each two of the N multi-level signals transmitted through the two data transmission channels to obtain a respective bit of the M bits of each binary data segment of the data signal based on comparison between the two corresponding multi-level signals.