The present application relates to a data bus system, its encoder/decoder and encoding/decoding method. The data bus encoder comprises: a bus-invert encoder for generating encoded data and invert-indication information by performing bus-invert encoding on data according to a predetermined bus-invert encoding scheme; a virtual bit-group generator for converting the invert-indication information into a virtual bit-group according to a predetermined code mapping; and an error-checking-and-correction encoder for generating an error-checking-and-correction code for a virtual word according to a predetermined error-checking-and-correction encoding scheme, wherein the number of error-checking bits is more than the number of error-correction bits at least by one in the predetermined error-checking-and-correction encoding scheme, and the virtual word includes the data to be output, the virtual bit-group corresponding to the data, and at least one padding bit of a fixed value, which is configured as required by the error-checking-and-correction encoding scheme.