Disclosed is a method for implementing link self-adaptation, comprising: a terminal device detecting channel quality, comparing the channel quality with a threshold, and when the channel quality exceeds the threshold, reporting channel quality information CQI; and a network device receiving the CQI information, and selecting a suitable transmission mode for downlink data transmission according to the CQI information. Further disclosed are a terminal device and a network device. By using the method and devices provided in the present invention, the spectrum utilization rate and system performance can be improved.