The invention discloses a data transmission method of a carrier wave of a power line, with frequency conversion and adaptive frequency selection. Communication band can be flexibly divided into a plurality of subcarriers through the arrangement of IFFT points and a sampling rate. When the carrier wave is distributed before the conversion of the IFFT, modulation data is just distributed on the subcarriers of 40 kHz to 500 kHz, and data on the other subcarriers is zero, thereby ensuring that the actual applied frequency range is 40 kHz to 500 kHz, without the need of the frequency spectrum displacement. A local end can figure out the channel condition of each subcarrier through the method of receiving a known signal sent by an opposite end, chooses the subcarrier which has the good channel condition to send a signal, and abandons the subscriber which has the channel condition. The invention can directly modulate the signal on the needed transmission band and carrier frequency, thereby reducing realization complexity and choosing the transmission band of the signal in an adaptive manner.