A signal processing method and system includes a baseband signal baseband signal processing module configured to perform slow envelope processing on a first signal, to obtain an envelope value E(n) of the first signal on which the slow envelope processing has been performed, obtain a phase value θ(n) based on E(n), where θ(n) and E(n) are in a linear relationship, and separate the first signal into a second signal and a third signal based on θ(n), where a phase difference between the second signal and the third signal is 2 θ(n), an amplifier configured to amplify the second signal and the third signal, and a synthesizer is configured to combine the amplified second signal and third signal to obtain a fourth signal.