Disclosed by the present disclosure are a power adjustment method and device and a power adjustment method based on a power line communication. The power adjustment method include: acquiring a plurality of noise values, wherein the plurality of noise values include: a plurality of power line communication (PLC) noise values corresponding to a plurality of communication sub-carriers, and a background noise value of an air conditioning unit itself; determining a plurality of noise powers corresponding to the plurality of noise values; generating a power adjustment data of the plurality of communication sub-carriers according to the plurality of noise powers; and regulating the transmitting power values of the plurality of communication subcarriers according to the power adjustment data.