The invention discloses a power supply device for a radio frequency power amplifier, the output end of a voltage controlled voltage source and the output ends of N current controlled current sources are connected in parallel to supply power to the radio frequency power amplifier. The power supply device also comprises an n th sampling unit and an n th filtering unit, wherein the n th sampling unit is used for sampling the sum of the output currents of the n-1 current controlled current sources and the voltage controlled voltage source to obtain an n th sampling signal; the n th filtering unit is used for filtering the n th sampling signal according to a predefined n th passband, and outputting the filtered n th sampling signal to an n th current controlled current source so as to control the output current of the n th current controlled current source. The n th passband is higher than an (n-1) th passband, and the switching frequency of the n th current controlled current source is higher than that of an (n-1) th current controlled current source, wherein N is an integer greater than or equal to 2, and n is a positive integer smaller than or equal to N. The invention also discloses a power supply method and system for the radio frequency power amplifier for improving integrated power supply efficiency.