A transmission method and system of the discrete multi-tone modulation data, the method includes: generating, at a transmitting side, a first bit table according to data to be transmitted, wherein items of the first bit table include carrying data information on each line during this data transmission; modulating and transmitting, at the transmitting side, the data according to the first bit table to a receiving side; and demodulating, at the receiving side, the received data according to the first bit table to obtain corresponding data. With the transmission method and system for discrete multi-tone modulation data provided in embodiments of the present invention, the line rate and the transmission power on lines can be dynamically and timely adjusted according to information ratio of the line transmission, by using a dynamic bit table (BIT table) to carry variable information on the data carried by lines, thereby saving power resource.