Disclosed herein is a power line channel-adaptive communications system and method. The power line channel-adaptive communications system includes a transmitting end, a channel-adaptive controller, and a receiving end. The transmitting end generates an adaptive chirp symbol signal of a preset type for transmission data according to a channel state of the power line, modulates the generated adaptive chirp symbol signal in any one of first and second transmission modes, and transmits the modulated adaptive chirp symbol signal via the power line channel. The channel-adaptive controller controls the type and transmission mode of the adaptive chirp symbol signal. The receiving end restores the transmission data by demodulating the adaptive chirp symbol signal, received via the power line channel, in any one of the first and second transmission modes according to the channel state of the power line.