The invention provides a radio frequency amplification method which comprises carrying out modulation on a first digital carrier signal by utilizing a digital envelope signal to produce a digital radio-frequency pulse signal having a first frequency; converting the digital radio-frequency pulse signal into an analog radio-frequency pulse signal; carrying amplification on the analog radio-frequency pulse signal to generate a radio-frequency output signal; converting an analog feedback signal from the radio-frequency output signal into a digital feedback signal; demodulating the digital feedback signal by utilizing a second digital carrier signal to generate an I signal and a Q signal; and generating an amplitude setting signal and a phase setting signal according to the I signal and the Q signal, wherein the amplitude setting signal is used for adjusting the amplitude of the digital envelope signal, and the phase setting signal is used for adjusting the phase of the first digital carrier signal. The second digital carrier signal has preset frequency deviation and preset phase deviation with respect to the first digital carrier signal. The invention also provides a radio frequency amplification system and a magnetic resonance imaging device.